System for predicting behavior of automotive vehicle and for controlling vehicular behavior based thereon

ABSTRACT

A system for detecting a physical amount of behavior of a vehicle includes, acceleration sensors arranged on at least two longitudinal axes of the vehicle, the vertical axis Of the vehicle and the lateral axis of the vehicle, a plurality of the acceleration sensors being disposed on each of the axes. A unit is provided for establishing a conversion equation for determining acceleration values of linear motion at an arbitrary point of the vehicle in the direction of each axis of an arbitrary coordinate system and acceleration values of rotational motion with respect to the each axis of the coordinate system while simultaneously using acceleration values detected by the acceleration sensors disposed on at least two of the vehicular longitudinal axes, the vertical axis and the lateral axis. There is also provided a unit for calculating the conversion equation to obtain the acceleration values of linear motion at an arbitrary point of the vehicle in the direction of each axis of the arbitrary coordinate system and acceleration values of rotational motion with respect to each axis of the coordinate system, a unit for establishing a motion equation expressing a plurality of freedom motions, and a unit for calculating the motion equation with the acceleration values of linear motion at an arbitrary point of the vehicle in the direction of each axis of the arbitrary axis of the arbitrary coordinate system and acceleration values of rotational motion with respect to the each axis of the coordinate system to obtain the physical amount associated with the behavior of the vehicle.

BACKGROUND OF THE INVENTION

The present invention relates to a system for detecting a physicalamount associated with the behavior or motion of an automotive vehicle,and a system for controlling vehicular behavior or motion on the basisof the detected physical amount associated with the vehicular behavior.More particularly, the invention relates to a system for detectingphysical data, such as acceleration, speed, angular acceleration, force,torque and so forth at a selected point on the vehicle, and forcontrolling the physical amounts in order to realize a desired vehicularbehavior or motion. Furthermore, the invention relates to a system whichincludes a reference model with predetermined response characteristicsfor controlling vehicular behavior to achieve the responsecharacteristics of the reference model with monitoring of the physicalamounts associated with the vehicular behavior.

As a typical model of behavior, the vehicular behavior of a vehicle bodyhaving steerable front wheels and rear wheels to be regarded as rigid,can be considered. Now, as shown in FIG. 1, a three dimensionalcoordinate system having x, y and z axes originated at the gravitycenter G of the vehicle body 1, is established. Regarding the vehicularbehavior about the gravity center as rigid body motion within a threedimensional space, the vehicular behavior can be classified as sixfreedom motions, which include: (1) linear motion along the x axis -longitudinal motion, (2) motion along the y axis - lateral motion, (3)motion along the z axis - vertical motion, (4) rotational motion aboutthe x axis - rolling motion, (5) rotational motion about the y axis -pitching motion, and (6) rotational motion about the z axis - yawingmotion.

These motions are closely associated with vehicular drivingcharacteristics. For example, yawing or rolling are important factorsfor determining vehicular driving stability. On the other hand, pitchingand the vertical motion are caused by undulation of the road surfaceand/or acceleration and deceleration of the vehicle and are motionswhich affect the riding comfort of the vehicle.

In advanced automotive technology in recent years, active controltechnologies, such as anti-lock brakes, traction control, four wheeldriving, four wheel steering, active suspension and so forth, forcontrolling vehicular characteristics as desired, have been developedand incorporated in modern vehicles. In such automotive controltechnologies, it is necessary to monitor vehicular behavior,particularly acceleration (angular acceleration), from time to time. Forthis purpose, a plurality of accelerations are often employed.

As a manner of monitoring vehicular behavior, JP-U-2-30780 (JapaneseUnexamined Utility Model Publication) discloses a method for detecting avehicular lateral acceleration and a yawing angular acceleration byemploying two acceleration sensors mounted respectively at front andrear portions of the vehicle, and arithmetically processing the outputsfrom the sensors. In addition, for vehicular behavior control, theposition of the gravity center of the vehicle, lateral slip angle ateach wheel and wheel slippage are considered as important factors. Thelateral slip angle is an angle derived on the basis of a ratio betweenlongitudinal speed and lateral speed of the vehicle and influences thevehicular steering characteristics. On the other hand, the wheelslippage is a value derived by dividing a difference between thevehicular body speed and the rotational speed of a wheel by thevehicular body speed. It has been known that there is an optimal rangeof wheel slippage for most effectively transmitting engine driving forceand braking force to a road surface. Among the active controltechnologies, there are some systems which optimally distribute enginedriving force to four wheels in order to reduce the lateral slip angletoward zero, and some systems which control engine outputs and/orbraking forces.

However, the vehicular behavior while traveling is typically a compositebehavior of the above-mentioned six freedom motions. Therefore, forenabling monitoring of the vehicular behavior satisfactorily, at leastsix acceleration sensors become necessary. In addition, since thesensors per se are mounted on the vehicular body, which is inacceleration, the detected values have to be processed with respect toan acceleration coordinate system. Furthermore, the detecting directionof the sensor can rotate according to rotation of the vehicle withrespect to the coordinate system of the road surface (static coordinatesystem). Therefore, correction by conversion of the coordinate system(for example, Eular's angular conversion) becomes necessary.

However, there is no prior art teaching which results in a solution forthe above-mentioned problem and thus there is a limit to the precisionof detection of the vehicular behavior. This can be an impediment toimplementation for further advanced vehicle control technologies.

U.S. Pat. No. 4,829,434, issued on May 9, 1989, for "Adaptive Vehicle"discloses a system which detects "driving behavior" of the driver,"environmental conditions", such as weather, distances from adjacentvehicles, and "vehicle driving conditions", such as vehicular speed,acceleration by means of sensors, and performs total feedback controlfor the vehicle by establishing an intelligent base with respect tothree basic conditions, i.e. the driving behavior, the environmentalcondition and the vehicle driving condition, by deriving an optimumcondition based thereon.

The control as proposed in the above-mentioned United States Patent isintended to provide improved cornering criterion for the vehicle.Therefore, once lateral slip or spinning of the vehicle is initiated,this system will have no effect.

Here, in the theory of vehicular behavior, when a vehicle undergoeslateral slip or spinning exceeding a cornering criterion, the magnitudeof the lateral slip and spinning can be reduced by reversing thesteering toward the neutral position or beyond the neutral position(counter steering). On the other hand, when a substantial under-steeringis caused to make it difficult to pass the corner, applying side brakingfor causing locking of the rear wheels (spin-turn) will assist inreducing the cornering radius. Such a counter steering technique andspin-turning technique are both highly advanced skills which aredifficult to perform for the average driver. Namely, in the case ofcounter steering, it requires a lot of experience to exactly measure therequired angle of steering in the reverse direction. Also, a spin-turnis a very difficult driving technique which can be done only by driverswho have advanced skill.

SUMMARY OF THE INVENTION

It is a first object of the present invention to provide a system whichpredicts forthcoming vehicular behavior by detecting a physical amountof motion in all directions at a selected point on a vehicle.

A second objection of the present invention is to provide a controlsystem which places the vehicle in a condition for desired behavior onthe basis of a detected physical amount associated with the vehicularbehavior.

A third object of the invention is to provide a control system whichperforms control according to behavior characteristics of a referencemodel different from the natural behavior characteristics of thevehicle.

In order to accomplish the first object of the invention, there isprovided a system for detecting a physical amount associated with thebehavior of an automotive vehicle using acceleration sensors fordetecting rotational motion and linear motion of the vehicle about atleast two of the vehicular longitudinal axes, the vertical axisextending through the gravity center of the vehicle and the lateral axisof the vehicle, for establishing motion equations with respect to eachof the axes at selected points on the vehicle while simultaneously usingacceleration values of at least two rotational motion detected by theacceleration sensors, and for deriving the physical amount associatedwith the behavior through calculation of the motion equations.

In order to accomplish the second object of the invention, there isprovided a system for controlling behavior of an automotive vehicleusing acceleration sensors for detecting acceleration values ofrotational motion and linear motion of the vehicle about thelongitudinal axis of the vehicle, the vertical axis extending throughthe gravity center of the vehicle and the lateral axis of the vehicle,for detection the rotational speed of wheel of the vehicle, fordetecting geometry of suspension of the vehicle and thus detectingvehicular height, for detecting steering angle through a steering wheel,and for controlling behavior of the vehicle on the basis of detectedacceleration, wheel speed, vehicular height and steering angle.

In order to accomplish the third object of the invention, there isprovided a system for controlling behavior of an automotive vehicle bydetecting an operational magnitude for controlling the steering system,the engine, the power train and the suspension system, detecting acontrol magnitude of actuation of the steering system, the engine, thepower train and the suspension system, detecting an amount associatedwith behavior in each of three dimensional directions of the vehicle,storing a standard behavior model while taking into consideration theoperational magnitude in a standard vehicle having predeterminedreference response characteristics and amounts associated with thecurrent behavior of the vehicle and outputting amounts associated withforthcoming behavior of the standard vehicle, predicting an amountassociated with behavior of the standard vehicle using the standardbehavior model with respect to input data of a detected currentoperational magnitude and the amounts associated with the currentbehavior of the vehicle, storing a behavior predicting model of thevehicle to be actually controlled, taking the operational magnitude andamounts associated with the behavior of the vehicle to be actuallycontrolled as input data, and outputting an amount associated with aforthcoming behavior of the vehicle in response to the input data,predicting an amount associated with the behavior of the vehicle to beactually controlled using the behavior predicting model of the vehicleto be actually controlled based on the detected current operationalmagnitude and the amounts associated with the behavior, comparing thepredicted values of the amount associated with the behavior of thestandard vehicle predicted and the predicted values of the amountsassociated with the behavior of the vehicle to be actually controlledfor detecting a difference of the predicted amounts, comparing thevalues of amounts associated with the behavior of the vehicle to beactually controlled and the value of the predicted amount of thebehavior of the standard vehicle to derive the difference therebetween,and responding to the difference of the predicted values of the behaviorof the standard vehicle exceeding a predetermined value by adjusting acontrol magnitude of the vehicle in a direction for reducing thedifference.

In the preferred embodiment, various physical amounts, such as forcesalong the axes (longitudinal, lateral, vertical) of the vehicle,accelerations, speeds or velocities, torques around respective axes(pitching, rolling, yawing), angular accelerations, and angularvelocity, associated with the vehicular behavior can be derived byarithmetically processing outputs of six acceleration detecting devicesmounted on selected positions of a sprung mass (vehicular body) of thevehicle.

On the other hand, by enabling exact detection of the vehicular bodybehavior from time to time as well as the data associated with vehicularbehavior from the sensors, such as a wheel speed sensor, a steeringangle sensor and so forth, further advanced vehicular control can berealized.

Furthermore, in another embodiment of the present invention, it ispossible to achieve control equivalent to that of experienced driversupon occurrence of spinning, drifting, substantial under-steering inexcess of criteria of motions of the vehicle to recover the vehicularbehavior within the criteria. This contributes to safety and avoidanceof dangers.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an illustration showing directions of amounts associated withmotions potentially caused on an automotive vehicle;

FIG. 2 is a block diagram of one embodiment of a control systemaccording to the invention;

FIG. 3 is a block diagram showing steering, throttle and brake controlsection according to the invention;

FIG. 4 is an explanatory illustration showing the first embodiment oflayout of acceleration sensors on the vehicle;

FIG. 5 is an explanatory illustration showing the second embodiment oflayout of the acceleration sensors on the vehicle;

FIG. 6 is an explanatory illustration showing the third embodiment oflayout of the acceleration sensors on the vehicle:

FIG. 7 is an explanatory illustration showing a dynamic coordinatesystem and a static coordinate system to be employed for control in thepresent invention;

FIG. 8 is an explanatory illustration showing definition of coordinatevalues of the sensors and vectors;

FIG. 9 is an illustration showing definition of various variables inEular conversion;

FIG. 10 is block diagram showing hardware construction of a system forpredicting vehicular behavior;

FIG. 11 is an illustration showing manner or procedure for performingarithmetic operation for predicting behavior of the vehicle to beperformed by a microcomputer;

FIG. 12 is an illustration showing a process of arithmetic operation forpredicting behavior of the vehicle to be performed by the microcomputer,which is in series with the process of FIG. 11;

FIG. 13 is an illustration showing a process of arithmetic operation forpredicting behavior of the vehicle to be performed by the microcomputer,which is in series with the process of FIGS. 11 and 12;

FIG. 14 is an illustration showing a process of arithmetic operation forpredicting behavior of the vehicle to be performed by the microcomputer,which is in series with the process of FIGS. 11, 12 and 13;

FIG. 15 is an illustration showing a process of arithmetic operation forpredicting behavior of the vehicle to be performed by the microcomputer,which is in series with the process of FIGS. 11, 12, 13 and 14;

FIG. 16 is a schematic block diagram briefly showing overallconstruction of a control system (concentrated control) for theautomotive vehicle;

FIG. 17 is a schematic block diagram briefly showing overallconstruction of the control system (independent distributed control) forthe automotive vehicle;

FIG. 18 is a schematic and explanatory illustration showing overallcontrol system when various sensors are used;

FIG. 19 is an illustration showing coordinate values at wheel positionsrelative to the gravity center of the vehicle;

FIG. 20 is an illustration showing process for prediction of lateralslip angle;

FIG. 21 is an illustration showing process for predicting wheelslippage;

FIG. 22 is an illustration showing process for predicting travelingdirection and distance from a set timing;

FIG. 23 is a block diagram of an embodiment of a vehicular behaviorcontrol system utilizing a reference model;

FIG. 24 is an illustration showing construction of the steering anglecontrol section;

FIG. 25 is an illustration showing construction of a throttle controlsection;

FIG. 26 is an illustration of a construction of a differential mechanismin the throttle control section:

FIG. 27 is an illustration showing hydraulic pressure control sectionfor a brake;

FIG. 28 is an illustration showing connections between six freedomsensors and a control section;

FIG. 29 is an illustration showing vehicular behavior upon occurrence ofspinning;

FIG. 30 is an illustration showing vehicular behavior when countersteering is applied;

FIG. 31 shows an equilibrium of two dimensional forces on the vehicle inabsence of lateral slip of the gravity center of the vehicle;

FIG. 32 shows an equilibrium of two dimensional force at the occurrenceof lateral slip at the gravity center of the vehicle;

FIG. 33 shows an equilibrium of two dimensional forces upon applicationof counter steering for lateral slip at the gravity center of thevehicle;

FIG. 34 is an illustration showing process of control for corneringforce in the embodiment of the present invention;

FIG. 35 is an illustration showing process of prediction of vehicularbehavior in the embodiment of the invention;

FIG. 36 is an illustration showing process of control to be performed bythe embodiment of the invention;

FIG. 37 is an illustration showing driving behavior of the driver forpositively increasing the lateral slip angle at the gravity center inthe typical vehicle;

FIG. 38 is an illustration showing driving behavior of the driver forpositively increasing lateral slip angle at the gravity center in thetypical vehicle, during occurrence of over-steering;

FIG. 39 is an illustration showing process for correctingcharacteristics of a reference vehicle model; and

FIG. 40 is an illustration showing motion equation of the referencemodel and motion model of the vehicle to be controlled.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention will be discussed herebelow in terms of preferredembodiments relating an automotive vehicle.

FIG. 2 shows one embodiment of a system according to the presentinvention which includes an internal combustion engine 71, a front-rightwheel 72a, a front-left wheel 72b, a rear-right wheel 72c, a rear-leftwheel 72d, wheel speed sensors 73a, 73b, 73c and 73d for the respectivewheels, brake mechanisms 74a, 74b, 74c and 74d for the respectivewheels, suspension mechanisms 76a, 76b, 76c and 76d for the respectivewheels, a controlled differential gear unit 77, a steering wheel 78, anaccelerator pedal 79. a brake pedal 80, a steering control section 81, athrottle control section 82, a hydraulic braking pressure controlsection 83, a power transmission control section 84, six freedom motionsensor 85 and a control unit 86.

Each of the wheel speed sensors 73a, 73b, 73c and 73d comprises adetection gear for rotation with the associated wheel, and a magneticpick-up. The magnetic pick-up outputs a pulse train corresponding to arotational angle of the associated wheel. By measuring the interval ofthe individual pulses in the pulse train, the wheel speed at eachangular position can be detected.

Each of the brake mechanism 74a, 74b, 74c and 74d applies braking forcefor the corresponding wheel for deceleration. The brake mechanisms 74a,74b, 74c and 74d are provided with sensors for detecting brake linepressure during application of the brake.

The suspension mechanism 76a includes a damper (not shown) with a strokesensor 61a (not shown in FIG. 2) which may monitor the stroke of thesuspension mechanism 76a during vehicular travel. Other suspensionmechanisms 76b, 76c and 76d also include similar or the same strokesensors. The suspension mechanisms thus detect rolling and pitchingangles of the vehicle. At the same time, the suspension mechanisms mayalso detect variation of suspension alignment, such as the camber angle,toe angle and so forth.

The controlled differential gear unit 77 in the shown embodiment,comprises a limited slip differential gear unit which includes ahydraulic wet multi-plate clutch which can control the maximumdifferential torque limit. By this, torque distribution for drivingwheels can be freely adjusted between a normal unlimited state to alock-up state, in which the driving wheels are rigidly connected to eachother.

In FIG. 3, operations of the steering angle control section 81, thethrottle control section 82, and the hydraulic braking pressure controlsection 83 are illustrated. Each control section receives a demand fromthe driver through the steering wheel 78, the accelerator pedal 79 andthe brake pedal 80. The control sections derive the operationalmagnitudes of the steering angle, the throttle valve open angle and thebrake line pressure as operated by the driver to output such informationto the control unit 86. Simultaneously, the control sections receivecontrol commands from the control unit 86 for controlling the steeringmechanism 75, the engine 71 and respective brake mechanisms 74.

In the absence of the control command from the control unit 85, thesteering mechanism 75, the engine and respective brakes 74 arecontrolled directly by the demands from the driver.

FIG. 4 shows a proposed arrangement of the acceleration sensors in thesix freedom motion sensor 85. As shown in FIG. 4, acceleration sensors21 to 26 are arranged on three perpendicularly joined mounting stays 27to 29 intersecting at a point S as an origin, in such a manner that twoof the acceleration sensors are provided on each stay. When the xyzcoordinate axes are established as shown, the acceleration sensors 21and 22 on the mounting stay 27 (extending along x axis) detectacceleration in the z axis direction, the acceleration sensors 23, 24 onthe mounting stay 28 (extending along y axis) detect acceleration in thex axis direction and the acceleration sensors 25, 26 on the mountingstay 29 (extending along z axis) detect acceleration in the y axisdirection. Here, the directions of the accelerations to be detected bythe acceleration sensors, 21, 22: 23, 24: 25, 26 are not limited to theshown directions, but they can be arranged with the acceleration sensors21, 22 detecting the acceleration in the y axis direction, theacceleration sensors 23, 24 detecting the acceleration in the z axisdirection and the acceleration sensors 25, 26 detecting the accelerationin the z axis direction, or, in the alternative in respective oppositedirections (negative directions). Therefore, four possible ways ofmounting of the acceleration are available.

FIG. 5 shows another arrangement of the layout of the accelerationsensors. In the shown arrangement, the accelerations sensors 31 to 26are mounted on two perpendicularly joined mounting stays 37, 38extending along a selected one of two of three axes of the coordinatesystem (x and y axes directions in the shown embodiment). In the showncase, the mounting stay 37 is oriented along the x axis. Theacceleration sensors 35 and 36 for detecting acceleration in the y axisdirection and the acceleration sensors 31 and 32 for detectingacceleration in the z axis direction are mounted on the mounting stay37. Even in this case, there are three ways of selection of axes fororienting the mounting stays 37 and 38, such as alternating the y axisand the z axis. Also, there are two ways for mounting the accelerationsensors on the mounting stays, such as mounting the acceleration sensorsfor the z axis and the x axis on the mounting stay oriented in the yaxis direction.

FIG. 6 shows a further arrangement of the layout of the accelerationsensors, in which the acceleration sensors 31, 32 and 35, 36 arranged onthe mounting stay oriented in the x axis direction are replaced withmulti-axes type acceleration sensors 101 and 102. In FIG. 6, theacceleration sensors 101 and 102 are three axes detection typeacceleration sensors. However, in the shown case, the accelerationsensors directed to the y axis and the z axis are only active for use indetection of the accelerations. As can be appreciated, even in thiscase, there are several variations of combinations of the orientation ofthe mounting stays and arrangement of the acceleration sensors.

The sensor arrangement as shown in FIGS. 5 and 6 do not detect linearmotion in the direction of the x-axis but detect five freedom motion.These sensor arrangements can be used for a vehicle control systemwherein the linear motion in the direction of the x-axis need not beconsidered.

In addition, it is not always necessary to mount the sensors on thespecific mounting stays as illustrated in FIGS. 4 to 6. For instance, itis possible to mount the acceleration sensors on the vehicular bodyalong the imaginary x, y, z coordinate axes established with respect tothe vehicular body.

Next, a manner or process for predicting the vehicular behavior on thebasis of the detected values of the six acceleration sensors will bediscussed herebelow. In the following discussion, it is assumed that thevehicle (at least the vehicle body above the suspension) is a rigidbody. The following discussion will be given for the case in which theacceleration sensors are arranged in the layout illustrated in FIG. 4.

FIG. 7 shows four kinds of three dimensional coordinate systems employedin implementation of the process of prediction of the vehicularbehavior. At first, a coordinate system having the origin at the point Sand axes x₁, x₂ and x₃ is a dynamic coordinate system which shiftstogether with the sensors (accordingly with the vehicular body).Similarly, a coordinate system having its origin at the gravity center Gof the vehicle and three coordinate axes x, y and z, is a dynamiccoordinate system having a common direction to the coordinate systemhaving the x₁, x₂ and x₃ axes. A coordinate system having its origin ata point O other than the points S and G and three coordinate axes X, Yand Z is a static coordinate system stationary to the road surface. Thenegative direction of the Z axis is directed to the gravity center ofthe earth. A coordinate system having its origin at the point O andthree coordinate axes x₁, x₂ and x₃ is a rotational coordinate system,which has an axes orientation common to the axes x₁, x₂ and x₃ and x, y,z. Therefore, the rotational coordinate system will have no linearmotion component and will have only a rotational motion component.

At first, as shown in FIG. 8, it is assumed that the position vectors ofthe origin S of the coordinate system x₁ x₂ x₃ and the positions S₁ toS₆ of the sensors 21 to 26 with respect to the static coordinate systemXYZ are R_(s), R₁ to R₆ and position vectors for the positions S₁ to S₆are a₁ to a₆. In this case, the velocity vectors V_(s), V₁ to V₆ whichare obtained based on the relationship of the position vectors and bydifferentiating the position vectors, can be expressed by the followingequations. ##EQU1## wherein ω is an angular velocity vector of thedynamic coordinate system x₁ x₂ x₃ with respect to the statio coordinatesystem XYZ. The sign X represents external product.

By further differentiating V₁ to V₆, the accelerations A_(s), A₁ to A₆at the points S, S₁ to S₆ can be obtained from the following equations.

    A.sub.1 =A.sub.s +Aω.sub.s ×a.sub.1 +ω.sub.s ×(ω.sub.s ×a.sub.1)

    A.sub.2 =A.sub.s +Aω.sub.s ×a.sub.2 +ω.sub.s ×(ω.sub.s ×a.sub.2)

    A.sub.3 =A.sub.s +Aω.sub.s ×a.sub.3 +ω.sub.s ×(ω.sub.s ×a.sub.3)

    A.sub.4 =A.sub.s +Aω.sub.s ×a.sub.4 +ω.sub.s ×(ω.sub.s ×a.sub.4)

    A.sub.5 =A.sub.s +Aω.sub.s ×a.sub.5 +ω.sub.s ×(ω.sub.s ×a.sub.5)

    A.sub.6 =A.sub.s +Aω.sub.s ×a.sub.6 +ω.sub.s ×(ω.sub.s ×a.sub.6)                     (3)

wherein Aωs is the angular acceleration vector of the vehicle.

In the foregoing equations (2) and (3) , the components of externalproducts appear because the points S₁ to S₆ includes rotational motioncomponents with respect to the point S. Here, by deriving differences ofA₁ and A₂, A₃ and A₄, and A₅ and A₆, the following equations can beobtained.

    A.sub.1 -A.sub.2 =Aω.sub.s ×(a.sub.1 -a.sub.2)+[ω.sub.s ×(ωa.sub.1)-ω.sub.s ×(ω.sub.s ×a.sub.2)]

    A.sub.3 -A.sub.4 =Aω.sub.s ×(a.sub.3 -a.sub.4)+[ω.sub.s ×(ωa.sub.3)-ω.sub.s ×(ω.sub.s ×a.sub.4)]

    A.sub.5 -A.sub.5 =Aω.sub.s ×(a.sub.5 -a.sub.6)+[ω.sub.s ×(ωa.sub.5)-ω.sub.s ×(ω.sub.s ×a.sub.6)]                                          (4)

On the other hand, by obtaining external products of A₁ and a₂, A₂ anda₁, A₃ and a₄, A₄ and a₃, A₅ and a₆, and A₆ and a₅, and by derivingdifferences of the pairs similar to the above, the following equationscan be obtained. ##EQU2## Here, the unit vector of each axis of thecoordinate system x₁ x₂ x₃ are assumed as θ₁ (1,0,0), θ₂ (0,1,0) and θ₃(0,0,1). Then, the following relational equations between the positionvectors a₁ to a₆ can be established.

    (a.sub.1 -a.sub.2)=(l.sub.1 +l.sub.2)e.sub.1

    (a.sub.3 -a.sub.4)=(l.sub.3 +l.sub.4)e.sub.2

    (a.sub.5 -a.sub.6)=(l.sub.5 +l.sub.6)e.sub.3               (6)

With the foregoing relational equations and the formulae for vectorcalculation, the equations (4) and (5) can be modified to establish thefollowing equations:

    A.sub.1 -A.sub.2 =(l.sub.1 +l.sub.2)[Aω.sub.s ×e.sub.1 -{(ω.sub.s ·e.sub.1)ω.sub.s -ω.sub.s.sup.2 e.sub.1

    A.sub.3 -A.sub.4 =(d.sub.1 +d.sub.2)[Aω.sub.s ×e.sub.2 -{(ω.sub.s ·e.sub.2)ω.sub.s -ω.sub.s.sup.2 e.sub.2

    A.sub.5 -A.sub.6 =(h.sub.1 +h.sub.2)[Aω.sub.s ×e.sub.3 -{(ω.sub.s ·e.sub.3)ω.sub.s -ω.sub.s.sup.2 e.sub.3                                                   (7)

    e.sub.1 ×(l.sub.2 A.sub.1 +l.sub.1 A.sub.2)=(l.sub.1 +l.sub.2)e.sub.1 ×A.sub.s

    e.sub.2 ×(d.sub.2 A.sub.1 +d.sub.1 A.sub.2)=(d.sub.1 +d.sub.2)e.sub.2 ×A.sub.s

    e.sub.3 ×(h.sub.2 A.sub.1 +h.sub.1 A.sub.2)=(h.sub.1 +h.sub.2)e.sub.3 ×A.sub.s                                            (8)

wherein the sign represents internal product. Here, the accelerationvectors A₁ to A₆ at the points S₁ to S₆ are amount derived with respectto the static coordinate system XYZ. These can also be expressed bybreaking into components parallel to the axes x₁, x₂ and x₃ of thedynamic coordinate system by the following equations: ##EQU3##

Here, A₁₂, A₂₂, A₃₃, A₄₃, A₅₁ and A₆₁ are components monitored by thesix sensors.

On the other hand, the components of A_(s) and A.sub.ωs, can also beexpressed by breaking into components parallel to the axes x₁, x₂ and x₃of the dynamic coordinate system by the following equations.

    A.sub.s =A.sub.s1 e.sub.1 +A.sub.s2 e.sub.2 +A.sub.s3 e.sub.3

    Aω.sub.s =Aω.sub.s1 e.sub.2 +Aω.sub.s2 e.sub.2 +Aω.sub.s3 e.sub.3 (10)

Accordingly, from the foregoing equations (7) to (10), respectivecomponents of acceleration vector A, and the angular vector A.sub.ωsare, from A₁₂ and A₂₂, A_(s2), A.sub.ωs2, from A₃₃ and A₄₃, A_(s3) andA.sub.ωs3, and from A₅₁ and A₆₁, A_(s1) and A.sub.ωs1 being obtainedrespectively, expressed by the following equations: ##EQU4## Here, inthe equation (12), ω_(s1), ω_(s2) and ω_(s3) become necessary forderiving the angular accelerations A.sub.ωs1, A.sub.ωs2 and A.sub.ωs3.These values can be obtained by integrating the obtained angularaccelerations from time to time.

From the foregoing, the components of the linear acceleration vector andthe angular acceleration vector respectively parallel to the axes x₁, x₂and x₃ of the dynamic coordinate system at the selected point S on thevehicle can be determined. In general, the rotational components(angular velocity and angular acceleration) of the rigid body are equalat any point. Therefore, assuming that the vehicle (at least the vehiclebody above the suspension) is a rigid body, the components obtained asset forth above become the angular acceleration about the gravity centerof the vehicle. However, the linear components are differentiated atdifferent points on the vehicle. Therefore, as shown in FIG. 5, byestablishing the dynamic coordinate system xyz having its origin at thegravity center G of the vehicle, the position vector as from the point Gto the point S and the position vector R_(G) from the origin O of thestatic coordinate system to the gravity center G are derived. Then, thefollowing equation can be established.

    R.sub.s =R.sub.G +a.sub.s                                  (13)

By differentiating each side, the following equation can be established.

    V.sub.s =V.sub.G +ω.sub.s Xa.sub.s                   (14)

Here, V_(G) is the linear vector at the gravity center G. By furtherdifferentiation, the following equation can be obtained:

    A.sub.s =V.sub.G +Aω.sub.s ×a.sub.s +ω.sub.s ×(ω.sub.s ×a.sub.s)                     (15)

Here, A_(G) is the linear acceleration vector at the gravity center.Similarly to the process for the dynamic coordinate system x₁ x₂ x₃, byconsidering the equation (15) with respect to the broken componentsparallel to respective axes of the dynamic coordinate system xyz (alsoparallel to dynamic coordinate system x₁ x₂ x₃) having its origin at thegravity center G, and assuming a_(s) =(x_(s),y_(s),z_(s)) and A_(G)=(A_(Gx),A_(Gy),A_(Gz)), the following equations can be established forrespective components.

    A.sub.Gx =A.sub.s1 -(Aω.sub.s2 z.sub.s -Aω.sub.s3 y.sub.s)-[(ω.sub.s1 x.sub.s =ω.sub.s2 y.sub.s +ω.sub.s3 z .sub.s)ω.sub.s1 -ω.sub.s.sup.2 x.sub.s ]

    A.sub.Gy =A.sub.s2 -(Aω.sub.s3 x.sub.s -Aω.sub.s1 z.sub.s)-[(ω.sub.s1 x.sub.s =ω.sub.s2 y.sub.s +ω.sub.s3 z .sub.s)ω.sub.s2 -ω.sub.s.sup.2 y.sub.s ]

    A.sub.Gz =A.sub.s3 -(Aω.sub.s1 y.sub.s -Aω.sub.s2 x.sub.s)-[(ω.sub.s1 x.sub.s =ω.sub.s2 y.sub.s +ω.sub.s3 z .sub.s)ω.sub.s3 -ω.sub.s.sup.2 z.sub.s ]    (16)

On the other hand, the velocity vector V_(G) =(V_(Gx), V_(Gy), V_(Gz))can be obtained by integrating the equation (16).

Next, consideration is given for the problem in that, according torotation of the vehicle, the acceleration sensors also rotate to varythe detecting directions. When yawing motion about the z axis of thevehicle is detected by establishing the z axis in the orientation inalignment with the direction of gravity, if motion about the x axis(rolling) and/or motion about the y axis (pitching) are causedsimultaneously to cause inclination of the vehicle and thus to causeinclination of the detecting directions of the sensors, accuratemeasurement of the yawing cannot be achieved. The angular accelerationsAω_(s1), Aω_(s2) and Aω_(s3) obtained through the process set forthabove are respective components in the dynamic coordinate system x₁ x₂x₃, and linear accelerations A_(s1), A_(s2), A_(s3), A_(Gx), A_(Gy),A_(Gz) are respective components along the axes of the dynamiccoordinate system x₁ x₂ x₃ at a moment at which the vectors A_(s) andA_(G), are as defined in the static coordinate system XYZ. Accordingly,for obtaining components along the axes of the static coordinate systemXYZ, considering the coordinate system x₁ x₂ x₃ having the axesdirection equal to the coordinate systems x₁ x₂ x₃ and xyz and origincoincides with the point O, and making values obtained through theforegoing processes corresponding to this coordinate system, accuratedata should be obtained by performing conversion of the coordinatesystems between x₁ x₂ x₃ and XYZ.

FIG. 9 shows a process for conversion of correction of the inclination.Such conversion is generally referred to as Euler's conversion. Asillustrated, assuming that the angle formed by the X₃ axis and the Zaxis is θ, taking that the intersection line between the XY plane and X₁Y₁ plane as ON, the angle formed by the line ON and the X axis as φ, theangle formed by the line ON and the X₁ axis as ψ, the conversion from X₁X₂ X₃ coordinate system to XYZ coordinate system can be expressed by thefollowing equation: ##EQU5## wherein

    Ω.sub.11 =cosφcosψ-cosθsinφsinψ

    Ω.sub.12 =cosφcosφ-cosθsinψcosφ

    Ω.sub.13 =sin θsinψ

    Ω.sub.21 =sinφcosψ+cosθcosφsinψ

    Ω.sub.22 =sinφsinψ+cosθcosφcosψ

    Ω.sub.23 =sinθcosφ

    Ω.sub.31 =sinθsinψ

    Ω.sub.32 =-sinθcosψ

    Ω.sub.33 =cosθ

the linear acceleration vector A_(O) =(A_(Ox), A_(Oy), A_(Oz)) and theangular acceleration vector Aω_(O=) (Aω_(Ox), Aω_(Oy), Aω_(Oz)) arerespectively the amount with respect to the static coordinate systemXYZ. Here, the angles θ, φ and ψ can be obtained from the following.Assuming the angular velocity components in the direction of the axesX₁, X₂ and X₃ are ω_(x1), ω_(x2) and ω_(x3), the following relationalequations can be established:

    ω.sub.x1 =ωθcosψ+ωφsinθsinψ

    ω.sub.x2 =-ωφsinψ+ωφsinθcosψ

    ω.sub.x3 =ωψcosθ+ωφ        (18)

wherein

    ωθ=(dθ/dt), ωφ=(dφ/dt), ωψ=(dφ/dt)

Solving the foregoing equation (18), the following equation can beobtained.

    (θ≠0)

    ωθ=ω.sub.x1 cosψ-ω.sub.xz sinψ

    ωφ=(ω.sub.x1 sinψ+ω.sub.xz cosψ)/sinθ

    ωφ=ω.sub.x3 -ωφcos θ       (19a)

    θ=O)

    ωθ=ω.sub.x1 cosψ-ω.sub.xz sinψ

    ωθ+ωφ=ω.sub.x3                 (19b)

The angular velocities are ω_(x1) =ω_(s1), ω_(x2) =ω_(s2) and ω_(s3)=ω_(s3), and the values of θ, φ and ψ can be obtained by integrating theequation (19a) or (19b) depending upon whether θ≠0 or Therefore, thelinear accelerations, linear speeds and angular θ=0. accelerations andangular velocities can be derived through the foregoing process.

Then, the force applied to the gravity center G and the torque about theaxes will be determined. At first, with respect to the torque acting onthe vehicle, Euler's equation as set out with respect to the dynamiccoordinate system xyz is applicable. Therefore, it can be expressed bythe following equation. ##EQU6## Here, N_(G) is the torque, L is amagnitude of angular motion of the vehicle during motion, and I is aninertia matrix I_(ij) (inertia moment I_(ii), inertia multiplied productI_(ij) (i≠j).

By breaking the equation (20) for respective components along respectiveaxes and make the suffixes ij to correspond as 1→x, 2→y, 3→z, the torquevector N_(G) can be expressed using the angular velocity vector ω_(s)=(ω_(s1), ω_(s2), ω_(s3)) and the angular acceleration vector Aω_(s)=(Aωs1, Aω_(s2), Aω_(s3)), as follows:

    N.sub.Gx =(I.sub.xx Aω.sub.s1 + I.sub.xy Aω.sub.s2 + I.sub.xz ω.sub.s3)+[ω.sub.s2 (I.sub.zx ω.sub.s1 + I.sub.zy ω.sub.s2 + I.sub.zz ω.sub.s3)-ω.sub.s3 (I.sub.yx ω.sub.s1 + I.sub.yy ω.sub.s2 + I.sub.yz ω.sub.s3)]

    N.sub.Gy =(I.sub.yy Aω.sub.s1 + I.sub.yz Aω.sub.s2 + I.sub.yz ω.sub.s3)+[ω.sub.s3 (I.sub.yx ω.sub.s1 + I.sub.yy ω.sub.s2 + I.sub.yz ω.sub.s1)-ω.sub.s3 (I.sub.zx ω.sub.s1 + I.sub.zy ω.sub.s2 +I.sub.zz ω.sub.s3)]

    N.sub.Gz =(I.sub.zx Aω.sub.1 + I.sub.zy Aω.sub.s2 + I.sub.zz ω.sub.s3)+[ω.sub.s1 (I.sub.yx ω.sub.s1 + I.sub.yy ω.sub.s2 + I.sub.yz ω.sub.s3)-ω.sub.s2 (I.sub.xx ω.sub.s1 + I.sub.xy ω.sub.s2 + I.sub.xz ω.sub.s3)](21)

On the other hand, the force acting on the gravity center can beexpressed by utilizing the acceleration vector A_(G) =(A_(Gx), A_(Gy),A_(Gz)) and the mass weight M of the vehicle at the gravity center, asfollows:

    F.sub.Gx =MA.sub.Gx

    F.sub.Gy =MA.sub.Gy

    F.sub.Gz =MA.sub.Gz                                        (22)

In the foregoing, a discussion has been given for a model equation forcalculating and predicting each of the physical amounts associated withvehicular motion which can be calculated from the measured values of thesix acceleration sensors. Here, attention should be given to the factthat the process up to the equation (22), except for the assumption thatthe vehicle as a moving body is rigid, requires no further assumptionfor formulating the foregoing process. Namely, the foregoing equationscan be regarded as basic equations. The approximations necessitated dueto the capacity of the arithmetic operation of the microcomputer andlimitation of the motion of the vehicular motion should be regarded asessentially included in the present invention. When the dynamiccoordinate system x₁ x₂ x₃ is set by orienting the x₁ axis along thelongitudinal direction of the vehicle, the x₂ axis along the lateraldirection and the x₃ axis along the vertical direction, and if it can beassumed that the angular velocity about the x₁ axis (rolling angularvelocity) and the angular velocity about the x₂ axis (pitching velocity)are sufficiently small relative to the angular velocity about the x₃axis (yawing angular velocity), the foregoing equations (12) can beapproximated as follows: ##EQU7##

Similarly, in Euler's angular conversion of the foregoing equations(17), if the pole angle θ and the bearing angle ψ are sufficiently smallrelative to the bearing angle φ, approximations as cos θ≐1, cos ψ≐1, sinθ≐θ, sin ψ≐ψ can be adopted. Then, the coefficients for the conversionmatrix can be expressed by the following formulae:

    Ω.sub.11 ≐cosφ-ψ(sinφ)

    Ω.sub.12 ≐0

    Ω.sub.13 ≐θ·ψ

    Ω.sub.21 ≐sinφ+ψ(cosφ)

    Ω.sub.22 ≐-(sinφ)ψ+(cosφ)

    Ω.sub.23 ≐-θcosφ

    Ω.sub.31 ≐θ·ψ

    Ω.sub.32 ≐-θ

    Ω.sub.33 ≐1                                   (24)

These approximations of the model equations can be made depending uponthe required precision level.

All of the foregoing arithmetic operations can be performed by softwarein the microcomputer. FIG. 10 shows a hardware construction of thecontrol unit 86 for performing a prediction of the vehicular behavior,while FIGS. 11 to 15 show a series of flowcharts showing arithmeticoperations performed in the microcomputer.

At first, the overall hardware construction includes the accelerationsensors 21 to 26 as arranged at points S₁ to S₆ as shown in FIG. 4 (canbe arranged as shown in FIG. 5 or 6), signal amplifiers 41 to 46 forrespective sensors, AD converter 47 for converting six sensor outputs(analog signals) into digital signals (which may be realized as part ofthe functions of the microcomputer), a buffer 61 for temporarily storingthe input signals, and a microcomputer 48. The microcomputer 48comprises one or more CPU 48a, I/O 48b, ROM 48c, RAM 48d and otherperipheral LSI circuits. Depending upon required calculation speed,memory capacity, any desired hardware construction (for instance, aplurality of single chip microcomputers, digital signal processors orparallel processors which are capable of parallel processing) can beemployed.

As shown in FIGS. 11 to 15, in response to the turning ON of an ignitionkey as a main switch for initiating driving operation, the microcomputeris reset. Then, an initialization process is performed. Namely, datastored in RAM 48d, such as linear accelerations, angular accelerations,angular velocities and so forth, are cleared to "0". Then, at theresting condition of the vehicle before starting travel, theacceleration sensors 21 to 26 capable of detecting a DC component candetect only the gravitational accelerations g of the earth. Assumingthat the voltages g₁ to g₆ (analog signals) are output from theacceleration sensors 21 to 26 via the signal amplifiers 41 to 46, thesevoltages g₁ to g₆ are input to the microcomputer 48 through the ADconverter 47 and I/O 48b and then loaded to CPU 48a with the sensorcoordinate values h₁, h₂, l₁, l₂, d₁ and d₂. Then, the procedureprogrammed for performing arithmetic operation for the equation (11) isinitiated for deriving linear accelerations (g_(s1), g_(s2), g_(s3))(step 111). At the condition where the vehicle is resting, both of theangular accelerations and angular velocities are held at zero, thelinear accelerations (g_(s1), g_(s2), g_(s3)) derived at the step 111become the linear accelerations (g_(Gx), g_(Gy), g_(Gz)) at the gravitycenter. At this time, according to the calculation program based onEuler's angular conversion of the equation (17), the initial values ofthe Euler angles θ, φ and ψ are determined to establish a value (0, 0,g) in the reference coordinate system XYZ. The initial values of theEuler angles are stored in RAM 48d (step 112).

Then, once the vehicle starts to run, the acceleration sensors 21 to 26detect accelerations exerted on the vehicle. The signal amplifiers 41 to46 then are responsive to the outputs of the acceleration sensors 21 to26 to output voltages α₁ to α₆. These outputs are input to themicrocomputer 48 through the AD converter 47 and the I/O 48b and thenloaded on the CPU 48a together with the sensor coordinate values h₁, h₂,l₁, l₂, d₁ and d₂ stored in the ROM 48c. In response to this, thecalculation program based on the foregoing equations (11) and (12) isexecuted to derive the linear accelerations (A_(s1), A_(s2), A_(s3)) andangular accelerations (Aω_(s1), Aω_(s2), Aω_(s3)). The results of suchcalculation are stored in a selected area in the RAM 48d (step 113).Thereafter, the duration At of the first calculation cycle is loaded(stored in the ROM 48c or, in the alternative, is measured by aninternal timer of the microcomputer to perform the digital calculationexpressed by the following equations (step 114):

    ω.sub.s1 =Ω.sub.s1 +Aω.sub.s1 ·.increment.t

    ω.sub.s2 =Ω.sub.s2 +Aω.sub.s2 ·.increment.t

    ω.sub.s3 =Ω.sub.s3 +Aω.sub.s3 ·.increment.t (25)

wherein (ω_(s1), ω_(s2), ω_(s3)) are angular velocities to be derived,(Ω_(s1), Ω_(s2), Ω_(s3)) are angular velocities derived at one precedingcalculation cycle, and (Aω_(s1), Aω_(s2), Aω_(s3)) are angularaccelerations in the current calculation cycle. As the initial valuesfor these quantities, zeros are set. The angular velocity data derivedin the current cycle is stored in a selected area in the RAM 48d (step113) so that it may be loaded in the CPU 48a upon calculation of theequations (25) together with the angular accelerations (Aω_(s1),Aω_(s2), Aω_(s3)).

Next, from the ROM 48c, the coordinate data x_(s), y_(s) and z_(s)related to the gravity center G and the sensor position S are accessed.Also, from the RAM 48d, the linear accelerations (A_(s1), A_(s2),A_(s3)) and the angular accelerations (Aω_(s1), Aω_(s2), Aω_(s3))obtained through the steps 113 and 114 are loaded to execute thecalculation program according to the equation (16) to derive the linearaccelerations (A_(Gx), A_(Gy), A_(Gz)) at the gravity center. Theresultant linear accelerations are stored in the selected area in theRAM 48d (step 115). Similarly to the step 114, the duration At of thecalculation cycle is loaded to execute the following calculations:

    V.sub.Gx =FV.sub.Gx +A.sub.Gx ·.increment.t

    V.sub.Gy =FV.sub.Gy +A.sub.Gy ·.increment.t

    V.sub.Gz =FV.sub.Gz +A.sub.Gz ·.increment.t       (26)

wherein (V_(Gx), V_(Gy), V_(Gz)) are linear velocities to be obtained,(FV_(Gx), FV_(Gy), FV_(Gz)) are the linear accelerations derived at onepreceding calculation cycle, and (A_(Gx), A_(Gy), A_(Gz)) are linearaccelerations at the current calculation cycle. The initial values ofthese are set zero. The linear velocity data derived in the subsequentcalculation cycles are stored in the selected area of RAM 48d andupdated every cycle (step 116).

Next, the Euler angles θ, φ and ψ as initially set at the step 112 andthe angular velocities (ω_(s1), ω_(s2), ω_(s3)) derived through the step114 are loaded to execute a calculation program according to theequation (19) to derive the Euler angles θ, φ and ψ and the angularvelocity. Equations to be used are differentiated depending upon θ=0 orθ≠0. Particularly, when θ=0, since the intersection line ON of the XYplane of the coordinate system XYZ and the X₁ Y₁ plane of the coordinatesystem X₁ Y₁ Z_(l) is not established, φ and ψ cannot be defined. Theprocedure of calculation to be used at this time is illustrated in FIG.10. At first, with reference to the Eular angles Θ, Φ and Ψ of the onepreceding cycle of the Euler angle θ, φ and ψ loaded from the RAM 48d,judgement is made whether Θ= 0 (or can be approximately 0) or ≠0 (step117a). If Θ≠0, the calculation program according to the equation (19a)is executed in terms of Θ, Φ and Ψ and the angular velocities (ω_(s1),ω_(s2),ω_(s3)) to derive the angular velocities of the Euler angles θ,φ, ψ (step 117a₂), and further to derive the Eular angles Θ, Φ, and Ψthrough the following equations:

    θ=Θ+ωθ·.increment.t

    φ=Φ+ωφ·.increment.t

    ψ=Ψ+ωψ·.increment.t             (27)

wherein ω.sub.θ, ω.sub.φ, ω.sub.ψ are angular velocities of the Eulerangles, and At is the calculation cycle duration (117a₂).

On the other hand, when Θ=0, according to the equation (19b) with takingφ+ψ=ξ, the calculation program for deriving ω.sub.θ is executed based onthe angular velocity ω.sub.ξ (=ω.sub.φ +ω.sub.ψ and 9 (step 117a₁). Atthis time, in place of the equation (27), the angle 8 and M are derivedthrough the following equations:

    θ=Θ+ωθ·.increment.t

    ξ=Ξ+ωξ·.increment.t                (28)

where Ξ is the value of ξ of the one preceding cycle (step 117a₁).

Since the value of θ varies from time to time, it can become either =0and ≠0. At a certain moment where θ varies from ≠0 to =0, from the Eulerangles Φ and Ψ of the one preceding cycle, Ξ=Φ+Ψ is established forderiving Ξ through the equation (28) (steps 117b₂ to 117c₂). Conversely,at a certain moment where e varies from =0 to ≠0, an initial setting ismade for Φ=Ξ for Ψ=0 deriving the angular velocities of the Euler anglesφ and ψ through the equation (19a) and φ and ψ through the equation (27)(steps 117b₁ to 117c₁). Then, the linear accelerations (A_(Gx), A_(Gy),A_(Gz)), the straight velocities (V_(Gx), V_(Gy), V_(Gz)), the angularaccelerations (Aω_(s1), Aω_(s2), Aω_(s3)), and the angular velocities(ω_(s1), ω_(s2), ω_(s3)) are loaded from the RAM 48d in order to executethe calculation program according to the following equations: ##EQU8##wherein (X₁, X₂, X₃) are values of components of respective vectors onthe coordinate systems x₁ x₂ x₃ and xyz, and (Y₁, Y₂, Y₃) are valuesconverted into the coordinate system XYZ. It should be noted that thecoefficients in the matrix should be differentiated as follows dependingupon θ32 0 or θ≠0. (when θ≠0; step 117d₂)

    Ω.sub.11 =cosφcosψ-cosθsinφsinψ

    Ω.sub.12 =-cosφsinψ-cosθsinψcosφ

    Ω.sub.13 =sinθsinψ

    Ω.sub.21 =sinφcosψ+cosθcosφsinψ

    Ω.sub.22 =-sinφsinψ+cosθcosφcosψ

    Ω.sub.23 =-sinθcosφ

    Ω.sub.31 =sinθsinψ

    Ω.sub.32 =-sinθcosψ

    Ω.sub.33 =cosθ

    (θ=0:step 117d.sub.1)

    Ω.sub.11 -cosξ

    Ω.sub.12 =-sinξ

    Ω.sub.13 =0

    Ω.sub.21 =sinξ

    Ω.sub.22 =cosξ

    Ω.sub.23 =0

    Ω.sub.31 =0

    Ω.sub.32 =0

    Ω.sub.33 =1

Then, the linear accelerations A_(Ox), A_(Oy), A_(Oz)), the linearspeeds (V_(Ox), V_(Oy), V_(Oz)), the angular accelerations (Aω₀₁, Aω₀₂,Aω₀₃) and angular velocities (ω₀₁, ω₀₂, ω₀₃) at the gravity center withrespect to the coordinate system XYZ are derived in order to store inthe selected area in the RAM 48d.

Next, the microcomputer loads the angular accelerations (Aω_(s1),Aω_(s2), Aω_(s3)) and the angular velocities (ω_(s1), ω_(s2), ω_(s3))from the RAM 48d in order, and further loads the inertia moments I_(xx),I_(yy), I_(zz) and products of inertia I_(xy) (=I_(yx)), I_(yz)(=I_(zy)) and I_(zx) (=I_(xz)) from the ROM 48c to execute a calculationprogram according to the first equation of the equations (21) to derivethe torque N_(Gx) acting about the x axis and to store the resultantvalue to a selected area in RAM 48d. Similarly, with respect to thetorque, N_(Gy) acting about the y axis is derived through the secondequation in the equations (21), and the torque N_(Gz) acting about the zaxis is derived through the third equation in the equations (21).Respective values of the results of these calculations are stored inselected areas in the RAM 48d. On the other hand, the microcomputer 48loads the linear accelerations (A_(Gx), A_(Gy), A_(Gy)) at the gravitycenter from the RAM 48d and the mass weight M of the vehicle from theROM 48c to derive the forces (F_(Gx), F_(Gy), and F_(Gz)) acting alongrespective directions of the axes by multiplying respective linearaccelerations with the mass weight to store the selected areas of theRAM 48d (step 119).

Further, by repeating the calculation procedure at the step 117, thetorques (N_(Ox), N_(Oy), N_(Oz)) and the forces (F_(Ox), F_(Oy), F_(Oz))with respect to the coordinate system XYZ can be obtained. The resultantvalues of these calculations are stored in selected areas. Then, onecalculation cycle is terminated to return to the step 111 (step 120).

The calculation process from the step 111 to the step 120 is performedby the microcomputer with one calculation cycle (duration .increment.t).Here, it is not necessary to perform the calculation processes of thesteps 111 to the step 120 in order, but they can be carried out inparallel, if parallel processing is allowed, by providing a plurality ofprocessors.

Next, FIG. 16 is a conceptual illustration of the overall constructionof a vehicle control system. The shown construction includes thebehavior detecting system 100 as a subsystem forming part of the controlsystem. Namely, data at a certain timing, derived through thecalculation process of FIG. 10 and stored in the RAM 48d, such as,

angular accelerations: (Aω_(s1), Aω_(s2), Aω_(s3)), (Aω₀₁, Aω₀₂, Aω₀₃)

angular velocities: (ω_(s1), ω_(s2), ω_(s3)), (ω₀₁, ω₀₂, ω₀₃)

linear accelerations: (A_(s1), A_(s2), A_(s3)), (A_(Gx), A_(Gy), A_(Gz))(A_(Ox), A_(Oy), A_(Oz))

linear velocities: (V_(Gx), V_(Gy), V_(Gz)) (V_(Ox), V_(Oy), V_(Oz))

torques: (N_(Gx), N_(Gy), N_(Gz)) (N_(Ox), N_(Oy), N_(Oz))

forces: (F_(Gx), F_(Gy), F_(Gz)) (F_(Ox), F_(Oy), F_(Oz))

are read as required by the upper level control system as controlparameters.

FIG. 16 is illustrated as an embodiment including a single total controlsystem for concentrically performing control operations. However, thecontrol system can be established as an independent distributed typecontrol system, in which a plurality of control systems establishedindependently for mutually distinct control operations are provided. Insuch case, data obtained through the vehicular behavior detecting system100 may be supplied to a network system 130 established on the vehicle.Each control system obtains control necessary to control parameters onthe network system 130 in an asynchronous fashion and independently ofone another.

The method of prediction of the vehicular behavior as set forth abovesolely employs acceleration sensors as the sensor. In contrast, FIG. 18shows an embodiment employing wheel speed sensors 73a, 73b, 73c, 73d fordetecting rotational speeds of respective road wheels, steering anglesensors 50f, 50r for detecting actual steering angle at the front andrear wheels (50r is provided only for a vehicle having four wheelsteering system), vehicular height sensors 51fr, 51fl, 51rr, 51rl fordetecting suspension strokes at respective road wheels, a bearing ormagnetic declination sensor 52 for detecting the vehicular travelingdirection by detecting earth or terrestrial magnetism, in addition tothe 6 freedom motion sensor 85. The reference numeral 53 denotes adifferentiation circuit. Respective ones of these sensors have beenknown and employed in conventional vehicle control systems, navigationsystems and so forth. Therefore, the discussion for the constructionsthereof and the principles of their operations will be neglected.However, employing such a variety of sensors in the measurement ofvehicular behavior, control parameters important for performingvehicular control can be predicted.

FIG. 20 illustrates a process for predicting lateral slip angles β_(G),β_(fl), β_(fr), β_(rl), β_(rr) of the gravity center G and respectiveroad wheels (which will be hereafter distinguished by applying a suffixof fl for front left wheel, fr for front right wheel, rl for rear leftwheel and rr for rear right wheel) employing the six freedom motionsensor 85, the steering angle sensors 50f and 50r, and the vehicleheight sensors 51fr, 51fl, 51rr, 51rl. The lateral slip angle βtypically will affect the vehicular steering characteristics and can bederived based on the speed V_(ad) along the traveling direction orlongitudinal direction and the lateral speed V_(tr) from the followingequation: ##EQU9##

At first, the lateral slip angle β_(G) at the gravity center G can bederived through a calculation program according to the equation (30)setting V_(ad) =V_(Gx) and V_(tr) =V_(Gy) employing V_(Gx) and V_(Gy)derived through the step 116 of the process of FIGS. 11 to 15, or V_(ad)=V_(Ox) and V_(tr) =V_(Oy) employing V_(Ox) and V_(Oy) derived throughthe step 117, when the x axis of the coordinate system xyz is orientedin a direction coincident with the traveling direction of the vehicle.Then, for deriving the lateral slip angles at respective wheels, itbecomes necessary to derive the linear speed at respective wheels. Forthis purpose, the following vector calculation is to be considered.

Assuming that the position vector from the gravity center G to therotational center of one wheel is r_(T), the linear speed vector V_(T)of the wheel at the angular velocity vector ω_(s) of the entire body ofthe vehicle can be expressed by the following equation:

    V.sub.T =V.sub.G +ω.sub.G ×r.sub.T +V.sub.h    (31)

wherein V_(h) is relative speed vector when the unsprung mass includingthe wheel moves relative to the vehicle body (sprung mass - rigid body)through the suspension system. Here, as shown in FIG. 19, assuming thatthe motion of the suspension is strictly limited to the verticaldirection (z axis direction), the influence of displacement of thesuspension for the vector r_(T) becomes only the z axis component, andthe vector V_(T) should have only the z axis component. At this time,the position vectors and the speed vectors for respective ones of thefour wheels can be assumed as follows:

(front left wheel)

    r.sub.Tfl =(x.sub.Trl, y.sub.Tfl, z.sub.Tfl -h.sub.fl)

    V.sub.Tfl =(V.sub.xTfl, V.sub.yTfl, V.sub.zTfl -(dh.sub.fl /dt))

(front right wheel)

    r.sub.Tfr =(x.sub.Tfr, y.sub.Tfr, z.sub.Tfr -h.sub.fr)

    V.sub.Tfr =(V.sub.xTfr, V.sub.yTfr, V.sub.zTfr -(dh.sub.fr /dt))

(rear left wheel)

    r.sub.Trl =(x.sub.Trl, y.sub.Trl, z.sub.Trl -h.sub.rl)

    V.sub.Trl =(V.sub.xTrl, V.sub.yTrl, V.sub.zTrl -(dh.sub.rl /dt))

(rear right wheel)

    r.sub.Trr =(x.sub.Trr, y.sub.Trr, z.sub.Trr -h.sub.rr)

    V.sub.Trr =(V.sub.xTrr, V.sub.yTrr, V.sub.zTrr -(dh.sub.rr /dt))

wherein h_(fl), h_(fr), h_(rl) and h_(rr) are displacement in suspensionstroke at respective of front left, front right, rear left and rearright wheels, and (dh_(fl) /dt) , (dh_(fr) /dt) , (dh_(rl) /dt) ,(dh_(rr) /dt) are differentiated values (speed) thereof. Replacing thesein the foregoing equation (31), the following group of equations can beobtained for deriving each component of the linear speed vectorsV_(Tfl), V_(Tfr), V_(Trl), V_(Trr).

(front left wheel)

    V.sub.Tfl =(V.sub.Txfl, V.sub.Tyfl, V.sub.Tzfl)

    V.sub.Txfl =V.sub.Gx +[ω.sub.s2 (z.sub.Tfl -h.sub.fl)-ω.sub.s3 y.sub.Tfl ]

    V.sub.Tyfl =V.sub.Gy +[ω.sub.s3 x.sub.Tfl -ω.sub.s1 (z.sub.Tfl -h.sub.fl)]

    V.sub.Tzfl =V.sub.Gz +[ω.sub.s1 y.sub.Tfl -ω.sub.s2 x.sub.Tfl ]-(dh.sub.fl /dt)

(front right wheel)

    V.sub.Tfr =(V.sub.Txfr, V.sub.Tyfr, V.sub.Tzfr)

    V.sub.Txfr =V.sub.Gx +[ω.sub.s2 (z.sub.Tfr -h.sub.fr)-ω.sub.s3 y.sub.Tfr ]

    V.sub.Tyfr =V.sub.Gy +[ω.sub.s3 x.sub.Tfr -ω.sub.s1 (z.sub.Tfr -h.sub.fr)]

    V.sub.Tzfr =V.sub.Gz +[ω.sub.s1 y.sub.Tfr -ω.sub.s2 x.sub.Tfr ]-(dh.sub.fr /dt)

(rear left wheel)

    V.sub.Trl =(V.sub.Txrl, V.sub.Tyrl, V.sub.Tzrl)

    V.sub.Txrl =V.sub.Gx +[ω.sub.s2 (z.sub.Trl -h.sub.rl)-ω.sub.s3 y.sub.Trl ]

    V.sub.Tyrl =V.sub.Gy +[ω.sub.s3 x.sub.Trl -ω.sub.s1 (z.sub.Trl -h.sub.rl)]

    V.sub.Tzrl =V.sub.Gz +[ω.sub.s1 y.sub.Trl -ω.sub.s2 x.sub.Trl ]-(dh.sub.rl /dt)

(rear fight wheel)

    V.sub.Trr =(V.sub.Txrr, V.sub.Tyrr, V.sub.Tzrr)

    V.sub.Txrr =V.sub.Gx +[ω.sub.s2 (z.sub.Trr -h.sub.rr)-ω.sub.s3 y.sub.Trr ]

    V.sub.Tyrr =V.sub.Gy +[ω.sub.s3 x.sub.Trr -ω.sub.s1 (z.sub.Trr -h.sub.rr)]

    V.sub.Tzrr =V.sub.Gz +[ω.sub.s1 y.sub.Trr -ω.sub.s2 x.sub.Trr ]-(dh.sub.rr /dt)

Then, if the inclination of the vehicle relative to the road surface issufficiently small, the lateral slip angle at respective wheels can beexpressed by the following equations using the linear speed componentsin x and y axes direction and the actual steering angles X_(r) and X_(r)at the front and rear wheels. ##EQU10## wherein, in the case of avehicle having a two wheel steering system, λ_(r) is always 0.

Returning FIG. 20, the algorithm for predicting lateral slip angles atrespective wheels becomes as follows. At first, at a certain timing, themeasured values of the six freedom motion sensor 85, the steering anglesensors 50f and 50r, and the vehicle speed sensors 51fr, 51fl, 51rr,51rl are converted into digital signals through the AD converter 47(FIG. 10) and input to the microcomputer through I/O 48b and aretemporarily stored in the buffer 61 (step 201). Here, the outputsh_(fl), h_(fr), h_(rl) and h_(rr) are supplied to a differentiationcircuit 60 of an analog circuit construction to generate outputsproportional to the differentiated values (dh_(fl) /dt), (dh_(fr) /dt),(dh_(rl) /dt), (dh_(rr) /dt). These outputs of the differentiationcircuit 60 are also input to the microcomputer after digital conversion.Then, the measured value of the six freedom motion sensor 85 is read outfrom the buffer 61. Then, a similar procedure to the calculations ofFIGS. 11 to 15 is performed for deriving the linear speeds (V_(Gx),V_(Gy), V_(Gz)), and the angular velocities (ω_(s1), ω_(s2), ω_(s3)) atthe gravity center of the vehicle are derived (step 202). Then, themicrocomputer 48 loads the preliminarily stored coordinate values(x_(Tfl), y_(Tfl), z_(Tfl)), (x_(Tfr), y_(Tfr), z_(Tfr)), (x_(Trl),y_(Trl), z_(Trl)), (x_(Trr), y_(Trr), z_(Trr)) from the ROM 48c, themeasured values of the vehicle height sensors 51fr, 51fl, 51rr, 51rl,the differentiated values h_(fl), h_(fr), h_(rl), h_(rr) and (dh_(fl)/dt), (dh_(fr) /dt), (dh_(rl),/dt), (dh_(rr) /dt) from the buffer 61,and further loads the linear speeds (V_(Gx), V_(Gy), V_(Gz)) and theangular velocities (ω_(s1), ω_(s2), ω_(s3)) from the RAM 48d in order,to execute a calculation program according to the equation (33) forderiving the linear speed values (V_(Txfl), V_(Tyfl), V_(Tzfl)),(V_(Txfr), V_(Tyfr), V_(Tyfr)), (V_(Txrl), V_(Tyrl), V_(Tzrl)),(V_(Txrr), V_(Tyrr), V_(Tzrr)). The results of these calculations arestored in a selected area of the RAM 48d (step 203). Finally, themeasured values λ_(f) and λ_(r) are loaded from the buffer 61 and theresults of calculation at the step 202 are loaded from the RAM 48d tothe CPU 48a for execution of the calculation program according to theequations (34) to derive the lateral slip angles β_(fl), β_(fr), β_(rl),β_(rr) and then to store in the selected area in the RAM 48d.Thereafter, one cycle of calculation is terminated.

FIG. 21 illustrates the process for predicting the wheel slippage ateach wheel from time to time employing the wheel speed sensors 73a, 73b,73c and 73d in addition to the six freedom motion sensor 85, thesteering angle sensor 50f and 50r and the vehicle height sensors 51fr,51fl, 51rr and 51rl. In general, the wheel slippage is given as a ratioof the linear speed of the wheel in the traveling direction and thelinear speed of the vehicle body as derived through U_(T) =r_(T)ωT,assuming that the radius of the wheel is r_(T) and the rotation speed isω_(T). Similarly to the foregoing, each wheel is distinguished by asuffix. The wheel slippage values S_(Lfl), S_(Lfr), S_(Lrl) and S_(Lrr)are thus derived from U_(Tfl), U_(Tfr), U_(Trl) and U_(Trr) respectivelyderived from the wheel speeds as the linear speeds in the wheeltraveling directions, and the actual vehicle body linear speeds V_(Tfl),V_(Tfr), V_(Trl) and V_(Trr), and can be expressed by the followingequations:

    S.sub.Lfl =1-(U.sub.Tfl /V.sub.Tfl)

    S.sub.Lfr =1-(U.sub.Tfr /V.sub.Tfr)

    S.sub.Lrl =1-(U.sub.Trl /V.sub.Trl)

    S.sub.Lrr =1-(U.sub.Trr /V.sub.Trr)                        (35)

Here, the actual vehicle body linear speeds V_(Tfl), V_(Tfr), V_(Trl)and V_(Trr) can be expressed from the xy components of the values(V_(Txfl), V_(Tyfl), V_(Tzfl)), (V_(Txfr), V_(Tyfr), V_(Tzfr)),(V_(Txrl), V_(Tyrl), V_(Tzrl)), (V_(Txrr), V_(Tyrr), V_(Tzrr)) derivedthrough the equation (33) and the actual steering angles λ_(f) and λ_(r)of the front and rear wheels by the following equations:

    V.sub.Tfl =V.sub.Txfl cosλ.sub.f +V.sub.Tyfl sinλ.sub.f

    V.sub.Tfr =V.sub.Txfr cosλ.sub.f +V.sub.Tyfr sinλ.sub.f

    V.sub.Trl =V.sub.Txrl cosλ.sub.r +V.sub.Tyrl sinλ.sub.r

    V.sub.Trr =V.sub.Txrr cosλ.sub.r +V.sub.Tyrr sinλ.sub.r (36)

Returning to FIG. 20, the algorithm for predicting the wheel slippage ateach wheel is as follows. At first, the measured values of theabove-mentioned sensors including the six freedom motion sensor 85 areconverted into digital signals through the AD converter 47 and input toI/O 48b of the microcomputer for temporary storage in the buffer 61(step 211). Then, in a similar procedure to the steps 112 and 113 ofFIG. 14, based on the measured values of the six freedom motion sensor85, the linear speeds (V_(Txfl), V_(Tyfl), V_(Tzfl)), (V_(Txfr),V_(Tyfr), V_(Tzfr)), (V_(Txrl), V_(Tyrl), V_(Tzrl)), (V_(Txrr),V_(Tyrr), V_(Tzrr)) of respective wheels are derived (steps 212 and213). Then, using the actual steering angles λ_(f) and λ_(r) of thefront and rear wheels from the steering angle sensors 50f and 50r, thecalculation program according to the equation (36) is executed forderiving the linear speeds V_(Tfl), V_(Tfr), V_(Trl) and V_(Trr) and forstoring them in the RAM 48d (step 214). Finally, obtaining the measuredvalues ω_(Tfl), ω_(Tfr), ω_(Trl) and ω_(Trr) of the wheel speed sensors73a, 73b, 73c and 73d from the buffer 61, and loading the data of theradius r_(T) of the wheel from the RAM 48d, the linear speed convertedvalues U_(Tfl), U_(Tfr), U_(Trl) and U_(Trr) of the wheel speed arecalculated by multiplying those values. Thereafter, the linear speedsV_(Tfl), V_(Tfr), V_(Trl) and V_(Trr) are again loaded for executing thecalculation program according to the equation (35) to derive the wheelslippage values S_(Lfl), S_(Lfr), S_(Lrl) and S_(Lrr) and to store theresultant values in the RAM 48d. Thereafter, one calculation cycle isterminated (step 215).

FIG. 22 illustrates a process for predicting the distance and directionthat the vehicle has traveled, using the six freedom motion sensor 85and the bearing sensor 52. According to the algorithm shown in FIGS. 11to 15, the linear speeds (V_(Ox), V_(Oy) and V_(Oz)) on the referencecoordinate system XYZ can be derived on the basis of the measured valuesof the six freedom motion sensor 85. Similarly to the process set outabove, taking the duration of one calculation cycle of the microcomputerto be .increment.t, the traveled distances (L_(Ox), L_(Oy), L_(Oz)) canbe derived by again integrating the linear speeds (V_(Ox), V_(Oy),V_(Oz)) from the initially set time T=0, as expressed by the followingequations:

    L.sub.Ox =FL.sub.Ox +V.sub.Ox .increment.t

    L.sub.Oy =FL.sub.Oy +V.sub.Oy .increment.t

    L.sub.Oz =FL.sub.Oz +V.sub.Oz .increment.t                 (37)

wherein (FL_(Ox), FL_(Oy), FL_(Oz)) are values of the traveled distancescalculated at one preceding calculation cycle, which values areinitially set at 0 at T=0. Here, for example, if the z axis of thereference coordinate system XYZ is set to be oriented along thedirection of the gravity of the earth, and the bearing of theterrestrial magnetic pole as detected by the bearing sensor 52 ispresent on the ZX plane, the traveled distance in any direction andvariation of altitude from the set time to a desired time can becalculated from time to time.

The present invention has been discussed in detail hereabove. Though thepresent invention is intended to predict the behavior of the vehicle,the invention should not be limited to the algorithm of a behaviorprediction using the measured values of the acceleration sensors. Also,the present invention may be applicable for any moving body, such as aship, train, aircraft and so forth.

As set forth above, according to the preferred embodiment of theinvention, using at least two acceleration sensors for each axisdirection, and thus six acceleration sensors in total on the vehicleacting as a moving body, accelerations in the longitudinal, lateral andvertical directions of the vehicle can be determined. The microcomputeris then enabled to arithmetically determine the vehicular behavior, i.e.linear speeds (longitudinal, lateral and vertical motions), the angularacceleration about randomly set coordinate axes, and angular velocity(rolling, pitching and yawing) with the modeling equations establishedas internal software processes of the microcomputer. Furthermore, byadditionally providing the wheel speed sensors, the vehicle heightsensors, the steering angle sensors, and the bearing sensor, theimportant parameters for vehicular behavior, such as the lateral slipangle, the wheel slippage and so forth, can be predicted in real time.Accordingly, using a behavior detecting system including internalsoftware implementing a behavior predicting method according to theinvention as subsystem and combining the subsystem with the upper levelactive control system, such as an antilock brake, traction control, fourwheel drive control, four wheel steering control, active suspensioncontrol and so forth, as a part of such control systems, a more accuratevehicle control system can be constructed.

Similarly, by utilizing the bearing sensor to establish a system whichis capable of measuring vehicular traveling distance and/or altitudevariation and connecting with an upper level system, such as anavigation system, traffic information communication system and soforth, it will become possible to establish a high level drive assistsystem which can perform routing of the vehicle.

Next, an embodiment of a vehicular behavior control system whichachieves the third object of the present invention will be discussed.The shown embodiment of the control system is responsive to a vehicularcondition beyond the normal drive control criteria, such as spinning,drifting, and under steering, to perform control equivalent to the welltrained drivers according to a standard model response so that thevehicular condition can be restored within the criteria.

FIG. 23 is a block diagram of the embodiment of the automotive behaviorcontrol system according to the invention. In FIG. 23, the referencenumeral 231 denotes a device for detecting operational magnitude forcontrolling the steering system, the engine, the power train and thesuspension system of the automotive vehicle 1. 232 denotes a device fordetecting a control magnitude of a driving device (actuator) forcontrolling the steering system, the engine, the power train and thesuspension system of the automotive vehicle 1. 233 denotes a device fordetecting amounts associated with respective directions in the threedimensional space of the automotive vehicle. 234 denotes a standardmodel established on a standard vehicle having reference responsecharacteristics. 235 denotes a vehicular behavior prediction model whichis established by modeling response characteristics of the actualvehicle to be controlled. 236 denotes a comparing device for comparingthe value of the amount associated with the vehicular behavior predictedusing the standard model 234, and the value of the predicted amountusing the vehicular behavior predicting model to detect a difference ofthe predicted values. 237 is a comparing device for comparing the outputof the device 233 for detecting the amount associated with the vehicularbehavior and the predicted value of the standard model 234 for detectingthe difference therebetween. 238 denotes a control unit which receivesthe results of comparison in the comparing devices 236 and 237 and isresponsive to the difference between the predicted value of the standardmodel 234 and the predicted value of the behavior predicting model 237to make a judgement that the driving condition beyond the normal drivecontrol criteria to adjust the control magnitude of the driving devicefor reducing the difference between the predicted value of the standardmodel and the detected value representative of the amount associatedwith the actual vehicular behavior.

The standard model 234 and the behavior predicting model 235 bothreceives the detected operational magnitude, the control magnitude andthe amount associated with the vehicular behavior as inputs. Thestandard model 234 is a kind of simulated model of the vehicle havingoperational characteristics and response characteristics for aparticular control of well trained drivers. The standard model 234 ispreliminarily stored in the memory. The standard model is notnecessarily limited to a single model but can be plural so that thedriver may select a desired one. The behavior predicting model 235 isalso a simulated model established by preliminarily measuring theresponse characteristics for control of the vehicle to be actuallycontrolled. The behavior predicting model 235 is also stored in thememory.

The device for detecting the operational magnitude may detect thesteering angle of a steering wheel, a brake pressure, a throttle valveopen angle of the engine, or a shift position of the power transmission.

The driving device may include a steering angle control device 81, ahydraulic brake pressure control device 83, a throttle open anglecontrol device 82, a transmission control device 84, a differential gearcontrol device and so forth.

The device 233 for detecting the amount associated with the vehicularbehavior includes the 6 freedom motion sensor 85 and is capable ofdetecting the variation rate of the vehicular longitudinal acceleration,the vehicular longitudinal acceleration, the vehicular longitudinalspeed, the variation rate of the lateral acceleration of the vehicle,the lateral acceleration, the lateral speed, the variation rate of thevertical acceleration of the vehicle, the vertical acceleration of thevehicle, the vertical speed of the vehicle, the variation rate of therolling angular acceleration, the rolling angular acceleration of thevehicle, the rolling speed of the vehicle, the rolling angle of thevehicle, the variation rate of the pitching angular acceleration, thepitching angular acceleration of the vehicle, the pitching angular speedof the vehicle, the pitching angle of the vehicle, the variation rate ofthe yawing angular acceleration, the yawing angular acceleration of thevehicle, the yawing angular speed of the vehicle, the yawing angle ofthe vehicle and so forth.

The embodiment of the present invention which is applicable a thevehicle having two wheel steering for two front steerable wheels, afront engine and rear wheel drive power train layout, and an automatictransmission, will be discussed herebelow. Since the basic constructionis similar to that of FIG. 2, only the portions not illustrated in FIG.2 will be discussed herebelow.

FIG. 24 shows the construction of the steering angle control section 81.The steering angle control section 81 comprises an actual steering angleencoder 311 for detecting actual steering angle, a gear box 312 forreducing the revolution of a steering motor, a multi-plate wet clutch314, a gear box for reducing the revolution of a steering feelcorrection motor 315, a steering operational angle encoder 317 fordetecting the operated steering angle by the driver, an actual steeringangle control section 318, and a steering feel correcting section 319.The operation of the steering angle control section 81 will be discussedherebelow. When the driver carries out a steering operation through useof steering wheel 78, the operational magnitude of rotation of thesteering wheel is detected by the steering operational angle encoder 317and is input to a control unit 300. The control unit combines thesteering operational magnitude with various information to output asteering angle command for the actual steering angle control section318. The steering motor 313 is a kind of servo motor comprising anelectric motor and operates to adjust the detected value of the actualsteering angle encoder to the steering angle command of the control unit300. The steering mechanism 75 comprises a rack-and-pinion typeconstruction for differentiating toe angle of the front steerable wheelsthrough rotation of the steering shaft. The actual steering anglecontrol section 318 includes a power transistor 1181 for controllingcurrent, and an actual steering current detecting sensor 1182. Ingeneral, the output torque of the motor (electric motor) is proportionalto the input current. Here, by detecting the current input from abattery 320 to the steering motor 313 by the actual steering currentdetecting sensor 1182, the necessary torque for adjusting the actualsteering angle coincident with the steering command, namely the reactionforce on the road surface, can be detected. The control unit 300 feedsback the steering feel for the driver through the steering wheel 78 bymeans of the steering wheel correcting section 319, the steering wheelcorrection motor 315 depending upon the detected reaction force from theroad surface. On the other hand, the steering angle control section 81includes the multi-plate wet clutch 314. The clutch is responsive tofailure of the respective motors for engagement to directly connect thesteering shaft to the steering mechanism 75 so as to permit manualoperation of the steering mechanism directly through the steering wheel78. In view of this, the gear ratios of the gear boxes 312 and 316 areto be selected so as to allow the driver to manually perform a steeringoperation without requiring substantial operational force.

FIG. 25 shows the throttle control section 82. FIG. 26 shows adifferential mechanism employed in the construction of FIG. 25. A wire420 connected to the accelerator pedal 9 is secured to the differentialmechanism 422 as shown in FIG. 26. When the accelerator pedal 79 isdepressed and if the servo motor 424 is in a resting state, the throttlevalve 421 rotates together with the differential mechanism 422 toperform an action similar to that of the normal throttle valveconstruction. The throttle open angle is detected by means of a throttleposition sensor 423 and is input to the control unit 300. Now,discussion will be given for the case in which the servo motor 424 isdriven to rotate. When the accelerator pedal 421 is fixed, and the servomotor 424 is driven in the counterclockwise direction, the throttlevalve 421 is driven by the differential mechanism comprising bevel gearsto rotate in the clockwise direction (opposite to the motor drivingdirection). On the other hand, when the servo motor 424 is driven in theclockwise direction, the throttle valve 421 is driven in thecounterclockwise direction. Accordingly, by controlling the rotationalangle of the servo motor 424, the throttle valve open angle can becontrolled irrespective of the operation of the accelerator pedal of thedriver. The control unit 300 combines the throttle valve open angledetected by the throttle position sensor 423 with various information toperform prompt control for the throttle valve open angle by means of theservo motor 424. On the other hand, when a failure of the servo motoroccurs, since the throttle valve 421 can be driven by the acceleratorpedal 79, normal driving operation can be maintained.

FIG. 27 shows the hydraulic braking pressure control section 83 for asingle wheel. The hydraulic braking pressure control section 83comprises a brake pedal 80, a servo motor 432 coupled with a linkmechanism, a master cylinder 433, a master cylinder pressure sensor 434,a braking pressure control valve 435 and a wheel braking pressure sensor436. The link mechanism 431 is so constructed as to assure transmissionof the input from the brake pedal 80 and the servo motor 432 to themaster cylinder but not transmit the input from the servo motor 432 tothe brake pedal. The control unit 300 predicts the decelerationmagnitude required by the driver on the basis of the output of themaster cylinder pressure sensor 434. Though the shown embodiment isdesigned for predicting the deceleration demand through the hydraulicpressure generated in the master cylinder by depression of the brakepedal by the driver, it is also possible to predict the requireddeceleration magnitude by providing a brake pedal position sensor forthe brake pedal and detecting the displacement thereof. In the controlunit 300, a variety of information are combined with the decelerationdemand of the driver for deriving a necessary braking pressure controlcommand for establishing the predicted deceleration magnitude. Thebraking pressure control command is derived independently for eachwheel. The control unit 300 then controls the braking pressure at eachwheel so that the braking pressure detected by the wheel brakingpressure sensor may follow this command. On the other hand, even whenthe driver does not depress the brake, if the control unit 300 makes ajudgement that the braking force is required in such occasion that thevehicle enters into a corner at excessive speed, the servo motor 32 isoperated to transmit an operational force to the master cylinder 432through the link mechanism to situate the vehicle in the equivalentcondition to that when the driver depresses the brake pedal 80.

FIG. 28 shows the construction of the six freedom motion sensor 85. Thesix freedom motion sensor 85 is similar to those discussed with respectto FIGS. 4 to 6 and comprises six acceleration sensors 21 to 26 arrangedas shown in FIG. 4 in a fixed vehicular coordinate system orienting thex axis in the longitudinal direction, the y axis in the lateraldirection and the z axis in the vertical direction, a multiplier 452, aconverter circuit 453, two stage integration circuits 454 and 455, and adifferentiation circuit 456. As generally well known, the freedom in thevehicular behavior includes the rotational motion about the x axis(rolling), the rotational motion about the y axis (pitching), and therotational motion about the z axis (yawing) in addition to linear motionin respective ones of the x, y and z axes directions. These motionsoccur simultaneously to cause a composite vehicular behavior. Therefore,the information practically measured by the acceleration sensorsincludes all the six freedom motion component. Accordingly, taking theacceleration and speed in the x axis direction as a_(x) and v_(x), theacceleration and speed in the y axis direction as a_(y) and v_(y), theacceleration and speed in the z axis direction as a_(z) and v_(z), therotational angular acceleration and angular velocity about the x axis(rolling) as α_(x) and ω_(x), the rotational angular acceleration andangular velocity about the y axis (pitching) as α_(y) and ω_(y) and therotational angular acceleration and angular velocity about the z axis asα_(z) and α_(z), and the values detected by the six acceleration sensors21 to 26 as G_(a), G_(b), G_(c), G_(d), G_(e) and G_(f), the followingrelationships are established for the acceleration α_(x) in the x axisdirection and the rotational angular acceleration α _(y) about the yaxis (pitching). ##EQU11##

In the shown construction of the six freedom motion sensor 85, theforegoing calculation is made possible with the multiplier 452, theconverter circuit 453 and the integration circuit 545. The output of theintegration circuit 454 becomes the speed and angular speed information.On the other hand, the output of the integration circuit 455 becomes theposition information. The output of the differentiation circuit 456represents the acceleration variation rate information. These items ofinformation are supplied to the control unit. The control unit 300 usesthese items of information to detect the vehicular behavior condition,to predict the forthcoming vehicular behavior by solving the specificmotion equations for the specific vehicle while combining the detectingvehicular behavior condition with the driving operational information,such as steering angle made by the driver, the throttle valve openangle, the hydraulic braking pressure and so forth, and, also to predictthe behavior of the standard vehicle by solving the specific motionequations for the targeted vehicle (standard vehicle) to follow thecontrol thereto.

FIG. 29 shows a trace and a steering angle of the vehicle which performscornering at excessive speed to cause abrupt variation of the vehicularbehavior and thus cause spinning. FIG. 30 shows the trace and thesteering angle of the vehicle which performs high speed corneringthrough the same curve as FIG. 29 to cause abrupt variation of thebehavior, but to avoid the spinning using the counter steering to passthe corner. In FIGS. 29 and 30, the condition in (a) and (b) areidentical to each other. Dynamic equilibrium in two dimensional spacewhere the vehicle is cornering without causing lateral slip isillustrated in FIG. 31, dynamic equilibrium in two dimensional spacewhere the vehicle is cornering while causing lateral slip is illustratedin FIG. 32, and dynamic equilibrium in two dimensional space uponapplication of counter steering is illustrated in FIG. 33.

The vehicle 1 is subjected to cornering forces C_(fl), C_(fr), C_(rl)and C_(rr) generated on the left and right front wheels and left andright rear wheels, driving forces F_(arl) and F_(arr) acting on the leftand right rear wheels and increasing according to increase of thethrottle valve open angle, and braking forces F_(bfl), F_(bfr), F_(brl)and F_(brr) acting on the left and right front wheels and the left andright rear wheels. With these forces, a balance between the linearmotion in the y axis direction and the rotational motion about the zaxis is established. Assuming that the vehicle is cornering at aconstant speed V, the vehicular weight is m, the inertia moment aboutthe gravity center is I, the effective length from the gravity center ofthe vehicle to the front wheel is l_(f), the effective length from thegravity center of the vehicle to the rear wheel is l_(r), the frontwheel tread is l_(f), the rear wheel tread is l_(rt), the lateral slipangle at the gravity center of the vehicle as defined by tan β=V_(y)/V_(x) is β, and the steering angle is δ, the motion under theseconditions can be expressed by: ##EQU12## The cornering force isdetermined by the lateral slip angle with respect to the travelingdirection (direction of the speed V) of the vehicle. At the front wheel,the cornering forces are adjusted by the driver through the steeringangle. Assuming that the cornering power at the left and right frontwheels are K_(fl) and K_(fr), and the cornering power at the rear wheelsare K_(rl) and K_(rr), respective of the cornering forces can beexpressed by: ##EQU13## wherein β_(fl), β_(fr), β_(rl) and β_(rr) arelateral slip angles at respective ones of the left and right frontwheels and left and right rear wheels. Here, for the purpose ofsimplification of the disclosure, it is assumed that the lateral slipangles at the left and right front wheels and at the left and right rearwheels are the same.

Braking and driving force (commonly referring the braking force anddriving force) are controlled by the driver through the brake pedal andthe accelerator pedal. As is well known, the sum of the absolute valuesof the maximum cornering force to be generated by the tire at thecritical traveling condition and the braking and driving force ismaintained constant as long as the friction coefficient between the roadsurface and the tire is maintained unchanged. Now, if this constantvalue at the left and right front wheels are assumed to be F₁ and F_(r)and at the left and right rear wheels are assumed to be R_(l) and R_(r),the following equations can be established at the critical travelingcondition. ##EQU14##

In FIG. 31, the traveling direction (direction of the speed V) of thevehicle and the direction of the x axis are coincident with each other.At this condition, the vehicle has no speed component V_(y) in the yaxis direction, namely the condition β=0. Next, FIG. 32 shows thecondition where β<0. The reason why the rear wheels are thrown out ofthe outside of the corner, is for obtaining a wheel lateral slip angleto obtain correspondence with the centrifugal force due to absence ofthe steering mechanism. At this condition, if the absolute value of thebraking and driving force is increased by depressing the acceleratorpedal or applying the brake, the rear wheels brake beyond the criticalcondition. The motion equations for the linear motion along the y axisdirection and the rotational motion about the z axis are given asfollows: ##EQU15## The third and sixth elements of the equation (55)represent differences of the braking and driving forces between the leftand right front wheels and between the left and right rear wheels.Accordingly, as set forth above, by controlling the braking force at theleft and right front wheels using the braking pressure control section83 and by controlling the braking and driving force at the left andright rear wheels by the braking pressure control section 83 and thecontrolled differential gear unit 77, for directly controlling themoment about the z axis, the rotation about the z axis can be controlledin an active manner.

On the other hand, as can be appreciated from the equation (54), whenthe braking and driving forces (F_(arl) -F_(brl)) and (F_(arr) -F_(brr))are increased, the third and fourth elements in the equation (54) aredecreased to increase the lateral slip angle β. Furthermore, the fourthand fifth elements of the equation (55) are increased so the rotationalangular acceleration dω_(z) /dt about the z axis is increased to cause aspinning condition on the vehicle. Here, in order to avoid spinning, aswill be apparent from the equations (54) and (55), it is effective tocontrol the braking and driving force so as not be excessive and tocontrol the steering angle δ to reduce it into the negative range(opposite direction to the cornering direction, namely counter steering)to cause the rotational moment about the z axis to be reduced to zero orto a negative value with the cornering force generated by the frontwheels (FIG. 33).

In FIG. 34, the manner of implementation of the above-mentioned controlis illustrated. Discussion will be given for the front wheels which havea steering function at first and then for the rear wheels. In theequations (42) and (43), β+l_(f) ·ω_(z) /VC is the lateral slip angle atthe center of the tread of the front wheels, which can be detected byprocessing the information from the six freedom motion sensor 85 usingthe control unit 300. Here, by taking the lateral slip direction at thecenter of the front wheel tread in the vertical axis and the corneringforce in the horizontal axis, and setting the angle formed between thelateral slip angle at the center of the front wheel tread and the frontwheels as δ', the steering angle vector is considered. The projection ofthe steering vector for the axis of the cornering force is considered asactual cornering force. It should be apparent that δ' represents thesteering angle for generating the actual cornering force. Now, when thesteering angle δ' increases, the cornering force becomes maximum at acertain steering angle, and then decreases. Therefore, the steeringvector establishes the trace as illustrated in FIG. 34. In FIG. 34, thecondition (a) represents the case where normal control is performed, inwhich the steering angle δ' is positive and the cornering force is alsopositive. The conditions (b) and (c) represents the particular featureof the present invention, in which the steering angle is controlled. Inthe condition (b), the steering angle δ' is controlled to be zero tomake the cornering force zero. Furthermore, in the condition (c), thesteering angle δ' is controlled to be negative to generate a corneringforce in the direction opposite to a cornering direction. This isequivalent to realization of a counter steering which is a high drivingtechnique only possible for well trained drivers.

Next, a discussion will be given concerning the rear wheels. In thenormal driving conditions (d) and (e), with an increase of the drivingforce F, and the braking force F_(b), the cornering force is reduced.Furthermore, at the wheel spinning condition (f) due to excess tiredriving force, and the wheel locking state (g) due to excessive tirebraking force, the cornering force becomes zero. According to thepresent invention, such reduction of the cornering force is positivelyutilized so that the braking and driving force is controlled through thebraking pressure control section 83 and the throttle control section 82based on the vehicle speed and the wheel speed detected by the wheelspeed sensors 73a to 73d, and thus the cornering force is controlled.The method for controlling the cornering force by controlling thebraking force is naturally applicable for the front wheels which havebrakes.

According to the present invention, the control unit 300 activelyperforms a counter steering, applying braking only for the rear brakes,excessively opening the throttle valve to causing spinning of thedriving wheels and other control operations for controlling thecornering forces at respective wheels independently of each other so asto control the rotational moment about the z axis and thereby controlthe behavior condition of the vehicle on the basis of the vehicularbehavior information from the six freedom motion sensor 85, the wheelspeed from the wheel speed sensors 73a to 73d of respective wheels, thesteering angle information obtained from the steering control section81, the throttle valve open angle information obtained from the throttlecontrol section 82, and the braking pressure information obtained fromthe braking pressure control section 83. Of course, the controlleddifferential gear unit 77 and the transmission control section 84 areused for controlling the braking and driving force on the rear wheels.

With reference to FIG. 35, the prediction process of the vehicularbehavior within the control unit 300 will be discussed. The control unit300 is responsive to the rotational acceleration ω_(z) about the z axisfrom the six freedom motion sensor 85 (initiation of cornering, to resetthe integration circuit of the six freedom motion sensor 85 and re-startdetection. Based on the linear speeds V_(x) and V_(y) in the x and yaxes directions, the lateral slip angle β=arctan(v_(x) /v_(y)) at thegravity center is derived. Furthermore, with the rotation speed ω_(z)around the z axis and the steering angle input by the driver through thesteering wheel 78 (this is detected by the steering angle controlsection 81 acting as the steering angle sensor), the control unit 300detects the lateral slip angles at respective wheels. On the other hand,the control unit 300 detects the rotation angle (rolling angle) aboutthe x axis and the rotation angle (pitching angle) about the y axis fromthe outputs of the six freedom motion sensor 85 and thus detects thevehicular attitude for detecting the load on respective wheels.Furthermore, based on the information from the stroke sensors 51fr,51fl, 51rr and 51rl of the suspension mechanisms 76a, 76b, 78c and 76d,the information representative of vehicular attitude variation iscorrected. With the vehicular attitude variation thus derived and thedesign data of the suspension mechanism, variation of alignment, such ascamber angle change and toe angle change, is detected. In conjunctionwith the process set forth above, the wheel speeds at respective wheelsare detected by the wheel speed sensor and compared with the vehiclespeed detected by the six freedom motion sensor 85, and the wheelslippage at respective wheels are derived. Together with the lateralslip angle, load, alignment variation and wheel slippage at each wheel,a predicted driving force based on the throttle valve open angle demanddetected by the throttle control section 82 and the transmission gearposition detected by the transmission control section 84, the maximumdifferential limit torque at the rear wheel from the controlleddifferential gear unit, and non-linear characteristics of the tire andother variety of information, are used for deriving the cornering forceat each wheel. With the cornering force thus obtained, the braking forceand driving force, the motion equations internally stored in the controlunit 300, for the six freedom motion for the behavior characteristics ofthe standard vehicle as the target of control, the target of control forthe behavior of the vehicle is established.

In FIG. 36, the control process of the control unit, in which thevehicular behavior during a cornering condition at the critical speed isrepresented by the rotation speed about the z axis and as the standardvehicle, the neutral steering (the vehicle, behavior of which isdetermined solely by the steering angle and the speed) is selected. Therotation speed ω_(zO) about the z axis of the standard vehicle, which ispredicted in the manner shown in FIG. 35 and the rotation speed ω_(z)about the z axis of the vehicle to be controlled are compared. Whenω_(z) -ω_(ZO) >ξ (ξ is a random constant satisfying ξ>0), the controlunit 300 may make a judgement that over steering is caused on thestandard vehicle model, and may provide this information for the driverto give a caution. The control unit 300 then outputs a correctioncommand for the steering angle control section 81 to adjust the steeringangle δ to δ-.increment.δ. If the rotation speed ω_(z) is decreased, acorrection to make ω_(z) to follow ω_(zO) is continued. On the otherhand, when the rotation speed ω_(z) is not decreased despite decreasingof the steering angle for δ.increment., with continuing reduction of thesteering angle, the throttle valve open angle θ and the brake linepressure ζ are reduced through the throttle control section 82 and thebraking pressure control section 83 in a similar matter to the steeringangle δ. Furthermore, by the transmission control section 84 and thecontrolled differential gear unit 77, correction is performed so thatthe braking force at the left and right rear wheels and the drivingforce are properly reduced to increase the load on the front wheels andto increase the cornering force at the rear wheels to relatively reducethe rotational moment about the z axis. In addition, further correctionmay be performed by adjusting the steering angle to the directionopposite to the cornering direction (counter steering) to positivelygenerate a rotational moment in the opposite direction. Through theprocedure set forth above, ω_(z) can be controlled to follow ω_(zO).However, when ω_(z) cannot be reduced through all the effects set forthabove, the steering operation is performed up to the full lock positionin the counter steering direction and the braking pressures between thefront and rear wheels are maintained in the relationship frontwheel>rear wheel, the lateral slip angle β is controlled to approach toπ/2 to stop the vehicle.

Next, when ω_(zO) -ω_(z) <ξ' (ξ is a random constant satisfying ξ>0),the control unit makes a judgement that under steering is caused in thestandard model. Similarly to the above, the control unit 300 may providethis information to the driver for caution. The control unit 300 outputsa correction command to the steering angle control section 81 foradjusting the steering angle δ to δ+.increment.δ. If the rotation speedω_(z) about the z axis is increased, control for making ω_(z) to followω_(zO) is maintained. However, if the rotation speed ω_(z) about the zaxis is not increased despite increasing the steering angle for.increment.δ, the cornering force at the front wheels are regarded toreach the limits and then correction control for properly adjustingbraking forces and the driving forces at the left and right wheels areperformed by the throttle control section 82, the braking force controlsection 83, the transmission control section 84 and the controlleddifferential gear unit 77 so that the load at the front wheels isincreased to increase the cornering force at the front wheels and toreduce the cornering force at the rear wheels and thus the rotationalmoment about the z axis is relatively increased to make ω_(z) to followω_(zO). If ω_(z) is not increased despite of the all of the foregoingefforts, judgement is made that control is completely lost. In suchcase, it may be possible to fully close the throttle valve, to performshifting down of the transmission gear position for effecting enginebraking, and to apply braking pressure to lock the rear wheels to reducethe cornering force at the rear wheels to zero. By this, the rotationalmoment about the z axis is abruptly increased to initiate an actionequivalent to a so-called spin-turn. Here, if excessive rotational speedabout the z axis is induced, the foregoing control in response to oversteering may be initiated.

In general, the steering characteristics of the vehicle are set to belight under steering. Accordingly, over steering may be typically causedon a road having a substantially low friction coefficient, such as anicy road and so forth, or when the driver intentionally applies anexcessive braking force or driving force for each of the wheels(particularly for the rear wheels) to induce over steering, the controlillustrated in FIG. 36 may be effective for the former case. However,for the later case, it should be understood that the driver isattempting drifting to positively increase the lateral slip angle at thegravity center for making cornering with applying counter steering. Insuch case, the control unit 300 controls the lateral slip angle βfollowing the driver's driving operation in conjunction with performingcontrol for the rotational speed ω_(z) about the z axis. Namely, it isdesirable to vary the behavior characteristics of the standard vehiclewhich serves as the target for control, according to the driver'sdriving operation for avoid causing a sense of incongruity.

FIG. 37 shows a driver's operation for attempting to positively increasethe lateral slip angle at the gravity center in the typical vehicle, andFIG. 38 shows the driver's operation when not making such attempt. Here,it is assumed that the lateral slip angle is β0, the steering angle isδ0, the throttle valve open angle is θ0 and the brake line pressure isζ0 when over steering is detected. In FIG. 37, the reduction of thesteering angle δ is proper upon occurrence of over steering, and thethrottle valve open angle θ is increased in response thereto. Namely,the steering is operated in the reverse direction opposite to thecornering direction (counter steering) to attempt to positively inducethe moment in the opposite direction to the current rotating direction,and at the same time to decrease the cornering force at the rear wheelsby increasing the driving force at the rear wheels and thus to increasethe rotational moment about the z axis, for establishing a balance bymaking the rotational moment about the z axis zero. In contrast to this,in FIG. 38, in response to unexpected over steering, the driver appliesthe brake to increase the rotational moment about the z axis and thus toincrease the lateral slip angle at the gravity center of the vehicle.Furthermore, due to delay of operation timing of the steering angle δfor correction of the lateral slip angle β at the gravity center, a socalled Dutch roll is caused. As will be clear from comparison of FIGS.37 and 38, by detecting the lateral slip angle d, the steering angle δ,the throttle open angle θ and the braking pressure ζ, the driver's willcan be predicted with a relatively high accuracy.

FIG. 39 illustrates the operation of the control unit 300 uponoccurrence of over steering when the throttle valve open angle θ isevaluated as the driver's will. Initially, at the initiation of oversteering, the throttle valve open angle θ0 is detected. This initialvalue is referred as θ1. Then, the throttle valve open angle θ2, thelinear speed v_(x), the rotation speed ωz about the z axis, and thelateral slip angle β1 at the gravity center are detected at a timingafter elapsed time .increment.t. Then, dθ/dt is calculated. If dθ/dt>0,judgement can be made that the driver is intending to positively causeover steering. Then, according to the driver's will, the behaviorcharacteristics of the standard vehicle are changed to false oversteering characteristics. Practically, change is made for increasing theallowable rotation speed ω_(z) about the z axis, modifying the lateralslip angle β by adding a value derived by multiplying a variation of thethrottle valve open angle dθ/dt with a proper proportional constant K,to β1 to set as β =β1+K·dθ/dt, for example. Here, the control unit 300derives a standard steering angle control curve (θ, v_(x), ω_(z), β)while taking the throttle valve open angle θ, the linear speed v_(z) inthe z axis direction, the rotation speed ω_(z) about the z axis and thelateral slip angle β at the gravity center as parameters (here, for thepurpose of illustration, FIG. 39 shows example for right turning withtaking v_(z) as sole parameter). In the standard steering angle controlcurve (θ, v_(z), ω_(z), β), the throttle valve open angle, at which thesteering angle comes into the fully locked state, is assumed as θmax.This throttle valve open angle θmax is the maximum value to avoidspinning of the vehicle by steering angle control including a countersteering operation. Even when the driver attempts to increase thethrottle valve open angle beyond this value, the control unit 300 issuesthe control command for the engine 1 through the throttle controlsection 82 with correction for θ2=θmax. If θ2<θmax, the steering angleis corrected to be δ=f(θ2, v_(x), ω_(z), β). Subsequently repeating theprocess set forth above, the standard steering control curve is updatedfollowing the driver's will and will continue control to make thebehavior of the vehicle follow this characteristic. When the rotationspeed ω_(z) about the z axis becomes zero, a judgement is made that thevehicle is exiting from the curve and thus the correction control isterminated.

FIG. 39 shows an example for the case in which the driver is attemptinga drifting of the vehicle. However, for other driving operationsreflecting the driver's will, various operational magnitudes (operatedsteering angle, throttle valve open angle, the braking pressure and soforth) caused by the will of the driver are detected to predict thedriver's will to update the standard behavior characteristics forfollowing the driver's will and thereby to control the vehicularbehavior following thereto.

While the controls set forth above are performed, the control unit 300may display with display device 301 the correction values for thesteering angle, the braking pressure and the throttle valve open anglein real time for providing information concerning a difference ofoperational magnitude between the operational magnitude of the driverand that required for causing the demanded behavior on the vehicle. Whenjudgement is made that the difference of the operational magnitude ordifference of timing is sufficiently small, the driver may randomlyselect perform or not to perform controls.

FIG. 40 shows motion equations for the six freedom motion sensors whenthe behavior characteristics model 235 of the actual vehicle to becontrolled and the behavior characteristics model 234 of the standardmodel are approximated with a simpler behavior model. The valuesenclosed in the broken lines (having e (estimation) in the second digitof the suffix, such as Axet, Vxet, Xxet, Axem, Xxem) are predictedvalues for the vehicle to be controlled and the standard vehicle for atsecond later, based on the behavior of the vehicle to be controlled asdetected by the six freedom motion sensor 85.

Hereafter, the process for prediction of the vehicle to be controlledand the standard vehicle will be discussed in order. Prediction for thebehavior of the vehicle to be controlled can be performed by taking avariety of behavior information (having s (sensing) in the second digitof suffix, such as Axst, Vxst, Xxst, Axsm, Vxsm, Xxsm and so forth) asinitial values and integrating those values. In contrast to this, inprediction of the behavior of the standard vehicle, initially, the force(Fcx, Fcy, Fcz) acting along the x, y and z axes and the torque aboutthe x, y and z axes of the vehicle to be controlled, are derived on thebasis of the linear accelerations in the x, y and z axes directions, theangular acceleration about the x, y and z axes as detected by the sixfreedom motion sensor 85 and the behavior characteristics parameters(mass weight Mt, inertia moment about each axis Ixt, Iyt, Izt and soforth) of the vehicle to be controlled. Such forces and torques includecontrollable components and uncontrollable components, such as thestrength of the window. Then, solving the motion equations in terms ofthese forces, torques and the behavior characteristics parameters (massweight Mm, the inertia moment Ixm, Iym, Izm and so forth), the linearaccelerations and the angular acceleration with respect to respectiveaxes are predicted. Utilizing these predicted accelerations andpredicted angular accelerations, and taking the variety of behaviorinformation of the six freedom motion sensor 85, the behavior at.increment.t seconds later can be predicted by integration. In FIG. 40,although prediction is performed utilizing only current information,further precise control may be achieved by deriving the information byadditionally using the information of .increment.t seconds ahead by acenter finite difference method.

In the control unit 300, the behavior of .increment.t seconds later ofthe vehicle to be controlled and the behavior of .increment.t secondslater of the standard vehicle are compared to update the variety ofcontrol commands so as to reduce the difference therebetween.

The foregoing discussion has been given for a specific vehicle havingtwo front steerable wheels, and front engine and rear wheel drive powertrain layout and so forth. However, the method of detection of thebehavior in six freedom motion, control of the cornering force bycontrolling the braking and driving forces and control for positivelycontrolling the steering angle toward the direction opposite to thenormal cornering direction and so forth are applicable to any types ofvehicle, even for an electric vehicle.

As can be appreciated herefrom, the described embodiment is particularlyeffective in assuring safety by enabling high level driving techniquesequivalent to those made by well trained drivers even when the vehiclebehavior steering is driven in a condition exceeding the criteria tocause spinning, drifting, under and so forth.

What is claimed is:
 1. A system for controlling the behavior of anautomotive vehicle comprising:means for detecting operational magnitudefor controlling a steering system, an engine, a power train and asuspension system of the automotive vehicle; means for detecting acontrol magnitude of actuating means for controlling the steeringsystem, the engine, the power train and the suspension system of theautomotive vehicle; means for detecting an amount associated withbehavior in each of three dimensional directions of the vehicle; means,storing a standard behavior model, for taking said operational magnitudein a standard vehicle having predetermined reference responsecharacteristics, and amounts associated with the current behavior of thevehicle, and outputting amounts associated with a forthcoming behaviorof said standard vehicle; first predicting means for predicting anamount associated with behavior of said standard vehicle using saidstandard behavior model with respect to input data of a detected currentoperational magnitude and amounts associated with the current behaviorof the vehicle; means, storing a behavior predicting model of thevehicle to be actually controlled, for taking said operational magnitudeand amounts associated with behavior of the vehicle to be actuallycontrolled as input data, and outputting an amount associated withforthcoming behavior of said vehicle in response to said input data;second predicting means for predicting an amount associated with thebehavior of said vehicle to be actually controlled using the behaviorpredicting model of said vehicle to be actually controlled based on thedetected current operational magnitude and amounts associated with thebehavior; first difference detecting means for comparing values of theamounts associated with the behavior of the standard vehicle, predictedby said first predicting means, and the values of the amounts associatedwith the behavior of the vehicle to be actually controlled, predicted bysaid second predicting means, for detecting a difference between thepredicted amounts; second difference detecting means for comparing thevalues of amounts associated with the current behavior of the vehicleand the value of the amount of the behavior predicted by said firstpredicting means to derive a difference therebetween; and control means,responsive to the difference of the predicted values detected by saidfirst difference detecting means exceeding a predetermined value, foradjusting a control magnitude of said actuating means in a direction forreducing the difference detected by said second difference detectingmeans.
 2. A system as set forth in claim 1, which further comprisesmeans for displaying a predicted value difference when the predictedvalue difference detected by said first difference detecting meansexceeds a predetermined value.
 3. A system as set forth in claim 1,further comprising steering feel correcting means which controls areaction force at the steering wheel according to a reaction force froma road surface in operating of the steering system.
 4. A system as setforth in claim 1, whereinsaid operational magnitude detecting meansincludes means for detecting a steering angle of the steering wheel,means for detecting a hydraulic braking pressure, means for detecting athrottle valve open angle of the engine, and means for detecting a shiftposition of a power transmission; said actuating means including asteering control device, a hydraulic brake control device, a throttlevalve open angle control device, a transmission control device and adifferential gear control device; said means for detecting amountsassociated with behavior of the vehicle including at least one of meansfor detecting rotational speed of a wheel of the vehicle, means fordetecting a variation rate of longitudinal acceleration of the vehicle,means for detecting longitudinal acceleration of the vehicle, means fordetecting longitudinal speed of the vehicle, means for detectingvariation of lateral acceleration of the vehicle, means for detectinglateral acceleration of the vehicle, means for detecting speed in thelateral direction of the vehicle, means for detecting a variation rateof vertical acceleration of the vehicle, means for detecting verticalacceleration of the vehicle, means for detecting vertical speed of thevehicle, means for detecting variation rate of rolling angularacceleration of the vehicle, means for detecting rolling angularacceleration, means for detecting rolling angular velocity, means fordetecting rolling angle, means for detecting variation rate of pitchingangular acceleration of the vehicle, means for detecting pitchingangular acceleration, means for detecting pitching angular velocity,means for detecting pitching angle, means for detecting variation rateof yawing angular acceleration of the vehicle, means for detectingyawing angular acceleration, means for detecting yawing angular velocityand means for detecting yawing angle.
 5. A system as set forth in claim4, wherein said means for detecting amounts associated with the behaviorof the vehicle comprises:acceleration sensors disposed on at least twolongitudinal axes of the vehicle, the vertical axis of the vehicle andthe lateral axis of the vehicle, a plurality of said accelerationsensors being disposed on each of said axes; means for establishingconversion equation for determining acceleration values of linear motionat an arbitrary point of the vehicle in the direction of each axis of anarbitrary coordinate system and acceleration values of rotational motionwith respect to each axis of the coordinate system while simultaneouslyusing acceleration values detected by said acceleration sensors disposedon at least two of the vehicular longitudinal axes, the vertical axisand the lateral axis; means for calculating said conversion equation toobtain the acceleration values of linear motion at an arbitrary point ofthe vehicle in the direction of each axis of the arbitrary coordinatesystem and acceleration values of rotational motion with respect to eachaxis of the coordinate system; means for establishing a motion equationexpressing a plurality of freedom motions; and means for calculatingsaid motion equation with the acceleration values of linear motion at anarbitrary point of the vehicle in the direction of each axis of thearbitrary axis of the arbitrary coordinate system and accelerationvalues of rotational motion with respect to each axis of the coordinatesystem to obtain a physical amount associated with the behavior of saidvehicle.
 6. A system as set forth in claim 4, wherein said control meansgenerates an additional control magnitude to be provided for saidsteering control device in an opposite direction to a corneringdirection with reference to a speed vector at a center of a lineextending between left and right steerable wheels of the vehicledetected by said means for detecting an amount associated with behavior,when a negative cornering force is generated with respect to thecornering direction of the vehicle, and said control means generates anadditional control magnitude to be provided for said steering controldevice in the cornering direction with reference to a speed vector atthe center of the line extending between left and right steerable wheelsdetected by said means for detecting amount associated with behavior,when positive cornering force is generated with respect to the corneringdirection of the vehicle.
 7. A system as set forth in claim 4, whichfurther comprises means for varying input and output characteristics ofsaid standard behavior model according to a predetermined condition whenone of said steering angle, braking pressure and throttle valve openangle satisfies a predetermined condition.
 8. A system as set forth inclaim 4, which further comprises means for displaying the difference ofsaid operational magnitude and said control magnitude.
 9. A system asset forth in claim 4, which further comprises means for selectivelyactivating and deactivating said control means in response to a commandof the driver.
 10. A system as set forth in claim 4, wherein saidhydraulic brake control device controls braking pressure for each wheelindependently of the other.
 11. A system as set forth in claim 10,wherein said hydraulic brake control device includes a control systemfor controlling braking pressure for each wheel independently between alocking state and a non-locking state of the wheel.
 12. A system as setforth in claim 11, whereinwhen a yawing moment does not increase even ifthe steering angle is controlled to be increased, said hydraulic brakecontrol device controls the braking pressure for rear wheels to make therear wheels of a locking state, and when the yawing moment does notdecrease even if the steering angle is controlled to be decreased, saidhydraulic brake control device controls the braking pressure for frontwheels to make the front wheels of a locking state.
 13. A system as setforth in claim 11, whereinwhen a yawing moment does not increase even ifthe steering angle is controlled to be increased, said transmissioncontrol device and said differential gear control device controls a gearratio to make the rear wheels of a locking state, and when the yawingmoment does not decrease even if the steering angle is controlled to bedecreased, said transmission control device and said differential gearcontrol device controls the gear ratio to make the front wheels of awheel spin state.
 14. A system as set forth in claim 11, whereinwhen ayawing moment does not increase even if the steering angle is controlledto be increased, said transmission control device, said differentialgear control device and said throttle valve open angle control devicecontrols a driving torque to make the rear wheels of a locking state,and when a yawing moment does not decrease even if the steering angle iscontrolled to be decreased, said transmission control device and saiddifferential gear control device controls the driving torque to make thefront wheels of a wheel spin state.